Update WCAG references from 2.0 to 2.2

[Nayab-Gauhar]

Fixes #5411

Summary

Updated all outdated WCAG 2.0 references to WCAG 2.2 in the accessibility documentation page.

Changes

• Updated text from "WCAG 2.0 website" to "WCAG 2.2 website"
• Updated WCAG documentation links:
  • https://www.w3.org/TR/WCAG20/ → https://www.w3.org/TR/WCAG22/
  • https://www.w3.org/TR/UNDERSTANDING-WCAG20/ → https://www.w3.org/WAI/WCAG22/Understanding/
  • https://www.w3.org/WAI/WCAG20/quickref/ → https://www.w3.org/WAI/WCAG22/quickref/
  • https://www.w3.org/TR/WCAG20-TECHS/ → https://www.w3.org/WAI/WCAG22/Techniques/
• Updated link labels from "WCAG 2.0" to "WCAG 2.2"

All links now point to the current WCAG 2.2 standards and resources.

[webteam-app]

Nayab-Gauhar is not a collaborator of the repo