Fix iteration edit button color

What does this MR do?

• Add gl-reset-color! to overrides the default styling of gl-button class responsible for the blue color.
• Add .btn-link-hover:hover to issuable.scss to change the color of the Edit button on hover.
  • gl- utility class gl-hover-text-blue-800 doesn't seem to take effect. This needs a separate investigation. .btn-link-hover:hover is a temporary fix that needs to be removed later.

Screenshots

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

Issue #235158 (closed)