Fix expected behavior in mainline test

The number of commits in a branch merged into master shouldn't change
that we increment by a single version

Author: Mark Rydstrom

src/GitVersionCore.Tests/IntegrationTests/MainlineDevelopmentMode.cs

@@ -178,9 +178,9 @@ public void VerifySupportForwardMerge()
             fixture.MakeACommit("+semver: minor");
             fixture.AssertFullSemver(config, "1.1.0");
             fixture.MergeNoFF("support/1.0");
-            fixture.AssertFullSemver(config, "1.1.2");
+            fixture.AssertFullSemver(config, "1.1.1");
             fixture.MakeACommit();
-            fixture.AssertFullSemver(config, "1.1.3");
+            fixture.AssertFullSemver(config, "1.1.2");
             fixture.Checkout("support/1.0");
             fixture.AssertFullSemver(config, "1.0.4");