Remove overlap from file size limit tests

What does this MR do?

Makes the instance-level file size limit set in push_over_http_file_size_spec greater than the project-level limit set in push_rules_spec so that when the tests are run in parallel (e.g., on Staging) push_rules_spec doesn't trigger the application-level limit.

The application-level limit seems to take precedence and it has a different error message, which causes push_rules_spec to fail.

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

Closes #218620 (closed)