install-webdoc: keep installed RelNotes-*.txt

Otherwise URLs in the wild that point at older release notes will become
dangling.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: gitster

Documentation/install-webdoc.sh

@@ -30,7 +30,7 @@ for th in \
 do
 	h=`expr "$th" : "$strip_leading"'\(.*\)'`
 	case "$h" in
-	index.html) continue ;;
+	RelNotes-*.txt | index.html) continue ;;
 	esac
 	test -f "$h" && continue
 	echo >&2 "# rm -f $th"