Update design system (PLAYRTS-5514)

[pyby]

Description

SRGAppearance is updated with latest design system fonts and colors.
https://github.com/SRGSSR/srgappearance-apple

The grayD2 color is quite more brightness, and update reading with a better contrast.

Changes Made

• Update SRGAppearance to 5.2.2. version.
  • Fonts:
    • Update iOS SRGFontStyleH2 to regular bold.
    • Update iOS SRGFontStyleSubtitle1 to regular weight.
    • Update tvOS SRGFontStyleSubtitle1 to regular weight.
• Gray colors: Update grayC7 color to grayD2 (grayC7 is deprecated).

Checklist

• I have followed the project's style guidelines.
• I have performed a self-review of my own changes.
• I have made corresponding changes to the documentation.
• My changes do not generate new warnings.
• I have added tests that prove my fix is effective or that my feature works.
• I have reviewed the contribution guidelines.