build: fix typo in error message

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

scripts/git-submodule.sh

@@ -24,7 +24,7 @@ error() {
     echo "Alternatively you may disable automatic GIT submodule checkout"
     echo "with:"
     echo
-    echo " $ ./configure --disable-git-update'"
+    echo " $ ./configure --disable-git-update"
     echo
     echo "and then manually update submodules prior to running make, with:"
     echo