.gitlab-ci.yml: add EOF newline

Description

Somehow .gitlab-ci.yml ended up without an EOF newline; this MR adds it back. It also adds a section to .coafile to check .gitlab-ci.yml and .gitlab/ci/*.yml for whitespace errors.

API Changes and Justification

Backwards Compatible Changes

• This change does not modify any class/function/struct/type definitions in a public C header file or any Python class/function definitions
• This change adds new classes/functions/structs/types to a public C header file or Python module

Backwards Incompatible Changes

• This change modifies an existing class/function/struct/type definition in a public C header file or Python module
• This change removes an existing class/function/struct/type from a public C header file or Python module

If any of the Backwards Incompatible check boxes are ticked please provide a justification why this change is necessary and why it needs to be done in a backwards incompatible way.

Review Status

cc @adam-mercer

requested review from @adam-mercer

assigned to @karl-wette

added apinone infra_gitlab labels

approved this merge request

mentioned in commit 09306f0a

merged