Update check_copyright.sh (#13652)

Author: paulb777

scripts/check_copyright.sh

@@ -24,7 +24,7 @@ options=(
 list=$(git grep "${options[@]}" -- \
     '*.'{c,cc,cmake,h,js,m,mm,py,rb,sh,swift} \
     CMakeLists.txt '**/CMakeLists.txt' \
-    ':(exclude)**/Sources/ProtoGen' \
+    ':(exclude)Sources/ProtoGen' \
     ':(exclude)third_party/**' \
     ':(exclude)**/third_party/**')