Use firebase php-jwt 7

[didoda]

This is to fix a security advisory [https://packagist.org/security-advisories/PKSA-y2cr-5h3j-g3ys] on firebase/php-jwt < 7.

This fixes composer install too.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (f306050) to head (b7b7436).
⚠️ Report is 6 commits behind head on master.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@             Coverage Diff             @@
##              master      #114   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
- Complexity       277       278    +1     
===========================================
  Files             28        28           
  Lines            862       864    +2     
===========================================
+ Hits             862       864    +2     

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