fixrule(`aria_attribute_valid`, `a_link_purpose`): Update WCAG mapping to be consistent with ACT

[philljenkins]

• New Rule(s): List rule IDs

  • aria_attribute_valid
  • a_link_purpose

• New or modified help files:

  • a_link_purpose

This PR is related to the following issue(s):

• #1760

Additional information can be found here:

• ACTION artifact: ACT test results

Testing reference:

ACT test results:

• no failures listed for ruleID aria_attribute_valid
• no failures listed for ruleID a_link_purpose

I have conducted the following for this PR:

• [ ] I validated this code in Chrome and FF
• [ ] I validated this fix in my local env
• [ ] I provided details for testing
• [ ] This PR has been reviewed and is ready for test
• [ ] I understand that the title of this PR will be used for the next release notes.