Use 'everchanged' operator instead of 'changedafter' operator with 1970 (#598)

scripts/get_type_labels.py

@@ -27,8 +27,7 @@ def main(args):
         "order": "bug_id",
         "j_top": "OR",
         "f1": "bug_type",
-        "o1": "changedafter",
-        "v1": "1970-01-01",
+        "o1": "everchanged",
         "f2": "OP",
         "f3": "bug_type",
         "o3": "anyexact",