Fix type of `default_copts` (#1428)

With the cc rules removed from Bazel, the `copts` attribute is no longer a part of the build language proto

generatetables/generate_tables.go

diff --git a/generatetables/generate_tables.go b/generatetables/generate_tables.go
index be0f22e..3f5d3c7 100644
--- a/generatetables/generate_tables.go
+++ b/generatetables/generate_tables.go
@@ -70,7 +70,7 @@
 	// package arguments are also not listed in the proto file
 	types["default_hdrs_check"] = buildpb.Attribute_STRING
 	types["default_visibility"] = types["visibility"]
-	types["default_copts"] = types["copts"]
+	types["default_copts"] = buildpb.Attribute_STRING_LIST
 	types["default_deprecation"] = types["deprecation"]
 	types["default_testonly"] = types["testonly"]
 	types["default_applicable_licenses"] = buildpb.Attribute_LABEL_LIST