scripts/setlocalversion: clean up stale comment

Nobody has complained since 2a73cce ("scripts/setlocalversion:
remove mercurial, svn and git-svn supports"), so let's also clean up
the header comment accordingly.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/setlocalversion

@@ -2,7 +2,7 @@
 # SPDX-License-Identifier: GPL-2.0
 #
 # This scripts adds local version information from the version
-# control systems git, mercurial (hg) and subversion (svn).
+# control system git.
 #
 # If something goes wrong, send a mail the kernel build mailinglist
 # (see MAINTAINERS) and CC Nico Schottelius