fix: fix dashboard proto-gen shell script (#7897)

Fix the error below when running `npm run gen-proto` for dashboard:

```
meta.proto: This file contains proto3 optional fields, but --experimental_allow_proto3_optional was not set.
```

Approved-By: Gun9niR

Author: xx01cyx

dashboard/scripts/generate_proto.sh

@@ -14,6 +14,7 @@ else
 fi
 
 protoc --plugin=./node_modules/.bin/protoc-gen-ts_proto \
+    --experimental_allow_proto3_optional \
     --ts_proto_out=proto/gen/ \
     --proto_path=tmp_gen \
     --ts_proto_opt=outputServices=false \