Update type hint to align with docs and usage.

[joaufi]

Description

Updated the type hint for the verify kwarg of RequestsHTTPTransport to align with both the class documentation and intended usage of verify.

Testing

All tests pass. I'm happy to write a test that verifies both a bool and a str can be provided as an arg to verify but that seemed a bit overkill to me as MyPy should cover such usages in application code.

[codecov-commenter]

Codecov Report

Merging #285 (dfd0d1c) into master (9b131a1) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master      #285   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           26        26           
  Lines         2045      2045           
=========================================
  Hits          2045      2045           

Impacted Files	Coverage Δ
gql/transport/requests.py	100.00% <ø> (ø)

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[leszekhanusz]

Thanks for your PR 👍