[gn] fix minor mistake from f7cb1af

The script printed two `/` when one suffices.

Author: nico

llvm/utils/gn/build/sync_source_lists_from_cmake.py

@@ -123,7 +123,7 @@ def by_rev(files, key):
 
     # Output necessary changes grouped by revision.
     for rev in sorted(changes_by_rev):
-        commit_url = 'https://github.com/llvm/llvm-project/commit/'
+        commit_url = 'https://github.com/llvm/llvm-project/commit'
         print("[gn build] Port {0} -- {1}/{0}".format(rev, commit_url))
         for gn_file, data in sorted(changes_by_rev[rev].items()):
             add = data.get("add", [])