Change setup-ruby action to @v1 instead of a commit SHA.
Fix ruby-version reference -- the current setup actually runs the tests three times on ruby 2.6 each time. Instead it should reference the matrix.ruby version. You can confirm this by checking the test run of some other branch -- notice that the path when running bundle includes 2.6.x every time.
@v1
instead of a commit SHA.2.6.x
every time.