chore: Fix Generate Bindings CI

[maspe36]

Noticed two issues in our Generate bindings action.

1. We are trying to run git diff in rclrs/src (which is failing)

warning: Not a git repository. Use --no-index to compare two paths outside a working tree

2. The repo needs to be marked as a safe directory

fatal: detected dubious ownership in repository at '/__w/ros2_rust/ros2_rust'

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Not quite sure how to test this since the generate bindings action is on a timer 🤔

[esteve]

@maspe36 thanks! We can trigger a run after merging, no need to wait until the timer runs it.