Deprecate relaxed variants of media types

[bkoelman]

Deprecate the relaxed variants of JSON:API media type extensions, now that both NSwag and Kiota can handle media types containing double quotes.

Closes #1936.

QUALITY CHECKLIST

• Changes implemented in code
• Complies with our contributing guidelines
• Adapted tests
• Documentation updated

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.20%. Comparing base (dc50f7f) to head (b7031fb).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1966   +/-   ##
=======================================
  Coverage   92.20%   92.20%           
=======================================
  Files         437      437           
  Lines       14924    14924           
  Branches     2476     2476           
=======================================
  Hits        13760    13760           
  Misses        714      714           
  Partials      450      450           

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