fix: dev: [compose-core] declare all local variables in ``get_relation_data_file()``

bin/compose-core

@@ -3053,7 +3053,8 @@ export -f get_relation_data_dir
 
 
 get_relation_data_file() {
-    local service="$1" target_service="$2" relation_name="$3" relation_config="$4"
+    local service="$1" target_service="$2" relation_name="$3" relation_config="$4" \
+          new new_md5 relation_dir relation_data_file
 
     relation_dir=$(get_relation_data_dir "$service" "$target_service" "$relation_name") || return 1
     relation_data_file="$relation_dir/data"