branch: rework comments for future developers

For two cases in which we do not explicitly pass --track=<choice>
option down to the submodule--helper subprocess, we have comments
that say "we do not have to pass --track", but in fact we not just
do not have to, but it would be incorrect to pass any --track option
to the subprocess (instead, the correct behaviour is to let the
subprocess figure out what is the appropriate tracking mode to use).

Signed-off-by: Glen Choo <chooglen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

branch.c

@@ -549,9 +549,9 @@ static int submodule_create_branch(struct repository *r,
 		strvec_push(&child.args, "--track=inherit");
 		break;
 	case BRANCH_TRACK_UNSPECIFIED:
-		/* Default for "git checkout". No need to pass --track. */
+		/* Default for "git checkout". Do not pass --track. */
 	case BRANCH_TRACK_REMOTE:
-		/* Default for "git branch". No need to pass --track. */
+		/* Default for "git branch". Do not pass --track. */
 		break;
 	}