fix: Remove obsolete warning about cookie-size

[frederikprijck]

With the fact that we brought back cookie-chunking, we no longer want to output a warning message when the cookie exceeds the limit in size. Instead, we chunk the cookie in that case.

Additionally, since we added id token back in the session, there is a high chance of users hitting the limit, ending up with chunked cookies, and the fact that they will see an irrelevant warning message.

[frederikprijck]

Also removing this from the migration guide, as this is no longer accurate in the latest version of v4.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.68%. Comparing base (65ece16) to head (baeb49b).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2012      +/-   ##
==========================================
- Coverage   74.77%   74.68%   -0.09%     
==========================================
  Files          21       21              
  Lines        1859     1853       -6     
  Branches      287      286       -1     
==========================================
- Hits         1390     1384       -6     
  Misses        462      462              
  Partials        7        7              

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[MichaelCharles]

Currently, if you try to google the warning, nothing comes up, so for the sake of google-ability, the warning is,

The cookie size exceeds 4096 bytes, which may cause issues in some browsers. Consider removing any unnecessary custom claims from the access token or the user profile. Alternatively, you can use a stateful session implementation to store the session data in a data store.