Adjust expected string to JCasC 1.27

The GitJCasCCompatibilityTest extends RoundTripAbstractTest from the
configuration as code plugin test suite.

In JCasC 1.25, logging in the test was set to 'INFO' and the assertion
was testing that the 'INFO' level logging in that version of JCasC was
reporting that the submodule configuration contained two empty members.
The submodule configuration should not have contained two empty members,
but there was a bug in submodule configuration setting. That bug was
fixed earlier, but the bug fix did not change the INFO level logging of
configuration as code plugin 1.25.

In JCasC 1.27, test logging is set to 'FINER' and the logged statements
have changed significantly.  This assertion can now check that specific
values from the resource jenkins/plugins/git/configuration-as-code.yaml
are correctly reported in the JCasC 1.27 log file.

JCasC 1.27 allows much more precise checks that the submodule config
detail is correct.  The revised stringInLogExpected return value provides
that more precise confirmation.  Refer to 'mybranch-3' and 'mybranch-4'
in the resource jenkins/plugins/git/configuration-as-code.yaml

Thanks for the finer grained checks in the RoundTripAbstractTest and
the finer grained output from the configuration as code plugin!

Author: MarkEWaite

src/test/java/jenkins/plugins/git/GitJCasCCompatibilityTest.java

@@ -35,6 +35,6 @@ protected void assertConfiguredAsExpected(RestartableJenkinsRule restartableJenk
 
     @Override
     protected String stringInLogExpected() {
-        return "Setting class hudson.plugins.git.GitSCM.submoduleCfg = [{}, {}]";
+        return "Setting class hudson.plugins.git.SubmoduleConfig. branches = [mybranch-3, mybranch-4]";
     }
 }