RebaseCommand: Remove unnecessary fall through comments

It's easier to read a list of cases

	case A:
	case B:
	case C:
		... do something ...;
		break;

without intervening "// fall through" lines separating the cases.

This also makes it clearer that JGit uses "$FALL-THROUGH$", not "fall
through", to suppress fallthrough warnings in switch statements.
Eclipse does not pay attention to the second comment style.

Change-Id: I5279a727aee2868854d06bfcaac8cb8186b4299e
Signed-off-by: Jonathan Nieder <jrn@google.com>

org.eclipse.jgit/src/org/eclipse/jgit/api/RebaseCommand.java

@@ -275,9 +275,7 @@ public class RebaseCommand extends GitCommand<RebaseResult> {
 					throw new JGitInternalException(ioe.getMessage(), ioe);
 				}
 			case PROCESS_STEPS:
-				// fall through
 			case SKIP:
-				// fall through
 			case CONTINUE:
 				String upstreamCommitId = rebaseState.readFile(ONTO);
 				try {