WIP: Prevent text color of code content to be overridden by links

What does this MR do?

It just adds an !important to the style setting the text color of <code> thus protecting the code content color (red) from being overridden e.g. by the link text color (blue). See #199886 (closed) for the reasoning behind this.

There shouldn't be any noticeable side effects since linking code content is not widely used, but comes in handy at times.

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 #199886 (closed)