Use `dart run` instead of `dart pub run`, fix deprecation warning
diff --git a/protoc_plugin/Makefile b/protoc_plugin/Makefile
index bfdb5a3..a7556e3 100644
--- a/protoc_plugin/Makefile
+++ b/protoc_plugin/Makefile
@@ -96,7 +96,7 @@
 protos: $(PLUGIN_PATH) $(TEST_PROTO_LIBS)
 
 run-tests: protos
-	dart pub run test
+	dart run test
 
 clean:
 	rm -rf benchmark/lib/generated