CI: Adjust tests for GitHub runner

The group within the github image is `runner`, not `docker`.

Author: bastelfreak

spec/integration/transport/local_spec.rb

@@ -83,7 +83,7 @@ def make_target
           expect(runner.upload(target, file.path, dest, run_as: user).message).to match(/Uploaded/)
           expect(runner.run_command(target, "cat #{dest}", run_as: user)['stdout']).to eq(contents)
           expect(runner.run_command(target, "stat -c %U #{dest}", run_as:  user)['stdout'].chomp).to eq(user)
-          expect(runner.run_command(target, "stat -c %G #{dest}", run_as:  user)['stdout'].chomp).to eq('docker')
+          expect(runner.run_command(target, "stat -c %G #{dest}", run_as:  user)['stdout'].chomp).to eq('runner')
         end
 
         runner.run_command(target, "rm #{dest}", sudoable: true, run_as: user)