Correct instance limits docs for self-managed

The default limits noted on the page have remained outdated after merge
request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/27574
overrode the previous limit defaults from disabled to
specific values, for a certain subset of limits.

In the existing form the documentation claims no limits on CI/CD
subscriptions and CI Pipeline Schedules created under a project, but
this has been incorrect since the introduction, as the `default` plan
carries non-zero, positive defaults for such instance limits.

Also added a note on self-managed instance default limits for
group and project webhooks.

doc/administration/instance_limits.md

@@ -165,7 +165,7 @@ There is a limit when embedding metrics in GFM for performance reasons.
 
 On GitLab.com, the [maximum number of webhooks and their size](../user/gitlab_com/index.md#webhooks) per project, and per group, is limited.
 
-To set this limit on a self-managed installation, run the following in the
+To set this limit on a self-managed installation, where the default is `100` project webhooks and `50` group webhooks, run the following in the
 [GitLab Rails console](operations/rails_console.md#starting-a-rails-console-session):
 
 ```ruby
@@ -173,7 +173,7 @@ To set this limit on a self-managed installation, run the following in the
 # Plan.default.create_limits!
 
 # For project webhooks
-Plan.default.actual_limits.update!(project_hooks: 100)
+Plan.default.actual_limits.update!(project_hooks: 200)
 
 # For group webhooks
 Plan.default.actual_limits.update!(group_hooks: 100)
@@ -235,8 +235,8 @@ If a new pipeline would cause the total number of jobs to exceed the limit, the
 will fail with a `job_activity_limit_exceeded` error.
 
 - On GitLab.com different [limits are defined per plan](../user/gitlab_com/index.md#gitlab-cicd) and they affect all projects under that plan.
-- On [GitLab Starter](https://about.gitlab.com/pricing/#self-managed) tier or higher self-managed installations, this limit is defined for the `default` plan that affects all projects.
-  This limit is disabled by default.
+- On [GitLab Starter](https://about.gitlab.com/pricing/#self-managed) tier or higher self-managed installations, this limit is defined under a `default` plan that affects all projects.
+  This limit is disabled (`0`) by default.
 
 To set this limit on a self-managed installation, run the following in the
 [GitLab Rails console](operations/rails_console.md#starting-a-rails-console-session):
@@ -261,7 +261,7 @@ too many deployments fail with a `deployments_limit_exceeded` error.
 
 The default limit is 500 for all [self-managed and GitLab.com plans](https://about.gitlab.com/pricing/).
 
-To change the limit on a self-managed installation, change the `default` plan limit with the following
+To change the limit on a self-managed installation, change the `default` plan's limit with the following
 [GitLab Rails console](operations/rails_console.md#starting-a-rails-console-session) command:
 
 ```ruby
@@ -284,7 +284,7 @@ If a new subscription would cause the total number of subscription to exceed the
 limit, the subscription will be considered invalid.
 
 - On GitLab.com different [limits are defined per plan](../user/gitlab_com/index.md#gitlab-cicd) and they affect all projects under that plan.
-- On [GitLab Starter](https://about.gitlab.com/pricing/#self-managed) tier or higher self-managed installations, this limit is defined for the `default` plan that affects all projects.
+- On [GitLab Starter](https://about.gitlab.com/pricing/#self-managed) tier or higher self-managed installations, this limit is defined under a `default` plan that affects all projects. By default, there is a limit of `2` subscriptions.
 
 To set this limit on a self-managed installation, run the following in the
 [GitLab Rails console](operations/rails_console.md#starting-a-rails-console-session):
@@ -308,8 +308,8 @@ On GitLab.com, different limits are [defined per plan](../user/gitlab_com/index.
 and they affect all projects under that plan.
 
 On self-managed instances ([GitLab Starter](https://about.gitlab.com/pricing/#self-managed)
-or higher tiers), this limit is defined for the `default` plan that affects all
-projects. By default, there is no limit.
+or higher tiers), this limit is defined under a `default` plan that affects all
+projects. By default, there is a limit of `10` pipeline schedules.
 
 To set this limit on a self-managed installation, run the following in the
 [GitLab Rails console](operations/rails_console.md#starting-a-rails-console-session):