util: ignore_file should not allow files ending with '~'

ignore_file currently allows any file ending with '~' while it
seems that the opposite was intended:
a228a22fda

src/shared/util.c

@@ -1371,7 +1371,7 @@ bool ignore_file(const char *filename) {
         assert(filename);
 
         if (endswith(filename, "~"))
-                return false;
+                return true;
 
         return ignore_file_allow_backup(filename);
 }