test-bzr: do not use unportable sed '\+'

Using sed -e '/[0-9]\+//' to find "one or more digits" is not
portable.

Use the Basic Regular Expression '/[0-9][0-9]*//' instead.
Signed-off-by: NTorsten Bögershausen <tboegi@web.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

contrib/remote-helpers/test-bzr.sh

@@ -328,7 +328,7 @@ test_expect_success 'strip' '
 
   echo four >> content &&
   bzr commit -m four &&
-  bzr log --line | sed -e "s/^[0-9]\+: //" > ../expected
+  bzr log --line | sed -e "s/^[0-9][0-9]*: //" > ../expected
   ) &&
 
   (cd gitrepo &&