Revert unnecessary changes to CI configuration

See merge request gitlab-org/gitlab-ee!8822

Removed duplicate line from SelectsHelper

See merge request gitlab-org/gitlab-ee!8823

EE: Resolve various database deprecation warnings

See merge request gitlab-org/gitlab-ee!8818

Support older NGINX version forwarding the client certificate for smartcard auth

See merge request gitlab-org/gitlab-ee!8784

Resolve various database deprecation warnings

See merge request gitlab-org/gitlab-ce!23772

This was added by accident due to a CE and EE MR both modifying this
file in a slightly different way.

This reverts commit 2fc61b12, reversing
changes made to e26d96d3.

Refactor Project#create_or_update_import_data

See merge request gitlab-org/gitlab-ce!23701

Move more EE specific code out of CE code

See merge request gitlab-org/gitlab-ee!8424

Allow matching only the repo-root for CODEOWNERS

Closes #8593

See merge request gitlab-org/gitlab-ee!8708

Do not save user preferences on read-only mode

Closes #55024

See merge request gitlab-org/gitlab-ce!23698

This fixes two cases of EE specific code extending
ActiveRecord::Migration, instead of extending
ActiveRecord::Migration[4.2].

The use of `table_exists?` in the opclasses support initializer triggers
a deprecation warning. Using `data_source_exists?` removes this
deprecation.

Extending from ActiveRecord::Migration is deprecated, but was still used
in a bunch of places.

The use of `table_exists?` in the opclasses support initializer triggers
a deprecation warning. Using `data_source_exists?` removes this
deprecation.

Move EE code out of app/helpers and into ee/app/helpers

See merge request gitlab-org/gitlab-ee!8702

Instance level Maven endpoint (second attempt)

Closes #7769

See merge request gitlab-org/gitlab-ee!8757

Extending from ActiveRecord::Migration is deprecated, but was still used
in a bunch of places.

Resolve "Empty state shown when the group security dashboard request fails"

Closes #8704

See merge request gitlab-org/gitlab-ee!8703

Add basic implementation of CI/CD bridge job

See merge request gitlab-org/gitlab-ce!23730

Wait for push before trying to create a new MR

See merge request gitlab-org/gitlab-ce!23745

Fix creation query for pools repository

See merge request gitlab-org/gitlab-ce!23729

Send a notification email on mirror update errors

Closes #54650

See merge request gitlab-org/gitlab-ce!23595

[EE] Send a notification email on mirror update errors

See merge request gitlab-org/gitlab-ee!8801