docs: parameter of request.get is case-insensitive

[gthb]

Note case-insensitivity for request.get, as docs already do for response.get

[codecov]

Codecov Report

Merging #1373 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #1373   +/-   ##
======================================
  Coverage     100%    100%           
======================================
  Files           4       4           
  Lines         377     377           
======================================
  Hits          377     377

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