Bump webmock from 3.7.5 to 3.7.6

Bumps webmock from 3.7.5 to 3.7.6.

Changelog

Sourced from webmock's changelog.

3.7.6

• Suppressed keyword argument warnings in Ruby 2.7 in async-http adapter.

  Thanks to Koichi ITO

Commits

• e9544e8 Version 3.7.6
• 0fb300a Added MRI 2.7 support.
• 7e3b4ff Merge pull request #850 from koic/suppress_kwarg_warnings_in_ruby27
• 2392703 Suppress keyword argument warnings in Ruby 2.7
• See full diff in compare view