fix(docs): hardcode Tile deprecation, fix console errors

[evwilkin]

Closes #4339
Closes #4176
Closes #4340

FYI - Line changes linked due to additional prettier formatting changes.

This PR:

• Fixes console errors:

  • error thrown by missing key prop in CSSVariables table. (cssVariables.js line 15)
  • error thrown by use of class rather than className in the site footer. (footer.js line 270)

• Hard-codes "Tile" to be deprecated:

  • Adds "deprecated" label to the Sidenav item (sideNav.js line 169)
    • Explanation: sidenav label isn't added if either the React or Core examples aren't marked deprecated, this line bypasses that check specifically for the Tile component.
  • Adds inline alert to the top of each Tile docs page (mdx.js line 125)
    • Explanation: Inline deprecation alert is only added on Core page if examples exist in a /deprecated/ directory, this bypasses that specifically for the Tile component.
  • Adds TODO comments to remove these hard-coded updates when Core #7178 is merged. (sideNav.js && mdx.js)

[patternfly-build]

Preview: https://patternfly-org-pr-4341-site.surge.sh

[tlabaj]

Can we open a follow up issues so we don't forget to do this?

[evwilkin]

Thank you! Created here - #4343