Guzzle 7 is released, no beta test needed

[Nyholm]

We test with Guzzle 5 on "prefer-lowest".
We test with Guzzle 6 on PHP < 7.2
We test with Guzzle 7 on PHP ≥ 7.2

[Nyholm]

The CI failure is unrelated to this PR. It seams like they are related because of the release to Guzzle 7. I dont know the build sequence, but it seams like it is just CI that fails, but the library is working.

[codecov-commenter]

Codecov Report

Merging #2050 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #2050   +/-   ##
=========================================
  Coverage     93.12%   93.12%           
  Complexity     3736     3736           
=========================================
  Files           206      206           
  Lines          9954     9954           
=========================================
  Hits           9270     9270           
  Misses          684      684           

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[howardlopez]

Thanks @Nyholm! Yes, there were some failing CI elements with the release of Guzzle 7 that were addressed in another PR.