Enable rspec coverage job on MR push pipeline

Ref: #246884 (closed)

What does this MR do?

This MR re-enable our rspec:coverage job on MR push pipeline.

Why are we doing this?

Today we enabled our coverage_report_view feature flag in order to try out our code coverage feature on gitlab.com.

We monitored the rollout and discovered our feature only worked for MR introducing frontend changes.

It turned out, we disabled our coverage report job for backend changes in !35244 (merged).

Screenshot

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• [-] Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• [-] Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team