Docs: Remove mention of rails env changing logs

The different naming of production{,_json}.log depending on the rails
environment is not important or useful for end users, which this
documentation is aimed at.

Additionally, it was not well explained in these docs before. We decided
that it was better to remove these lines than to explain them better.

doc/administration/logs.md

@@ -63,9 +63,6 @@ Depending on your installation method, this file is located at:
 - Omnibus GitLab: `/var/log/gitlab/gitlab-rails/production_json.log`
 - Installations from source: `/home/git/gitlab/log/production_json.log`
 
-When GitLab is running in an environment other than production,
-the corresponding log file is shown here.
-
 It contains a structured log for Rails controller requests received from
 GitLab, thanks to [Lograge](https://github.com/roidrage/lograge/).
 Requests from the API are logged to a separate file in `api_json.log`.
@@ -216,9 +213,6 @@ Depending on your installation method, this file is located at:
 - Omnibus GitLab: `/var/log/gitlab/gitlab-rails/production.log`
 - Installations from source: `/home/git/gitlab/log/production.log`
 
-When GitLab is running in an environment other than production,
-the corresponding log file is shown here.
-
 It contains information about all performed requests. You can see the
 URL and type of request, IP address, and what parts of code were
 involved to service this particular request. Also, you can see all SQL