Apply darker color to headers and scan names

• Related issue: #196831 (closed)

What does this MR do?

This changes the font color of column headers and scan names from #707070 to #2E2E2E in secure features configuration (/:group/:project/security/configuration).

Screenshots

Before	After

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