Update .openhands_instructions with linting (#4165)

.openhands_instructions

@@ -3,6 +3,7 @@ OpenHands is an automated AI software engineer. It is a repo with a Python backe
 
 General Setup:
 - To set up the entire repo, including frontend and backend, run `make build`
+- To run linting and type-checking before finishing the job, run `poetry run pre-commit run --all-files --config ./dev_config/python/.pre-commit-config.yaml`
 
 Backend:
 - Located in the `openhands` directory