Update ping-protocol submodule & regenerate definitions.py with correct OMNISCAN450_SET_SPEED_OF_SOUND id

[Maexerich]

This is my first PR on a open-source codebase. I used AI to navigate the process but have manually reviewed everything to the best of my knowledge.

Summary

This PR:

1. Updates the lib/ping-protocol submodule reference to use the fixed protocol definitions
2. Regenerates brping/definitions.py with the corrected message ID (although not tracked by git).

Related Fix

Depends on: bluerobotics/ping-protocol# at commit hash: 629510

Changes

• .gitmodules: Updated submodule URL to point to fixed ping-protocol fork temporarily
• lib/ping-protocol: Now references commit with corrected OMNISCAN450_SET_SPEED_OF_SOUND ID
  (- brping/definitions.py: Regenerated; now contains OMNISCAN450_SET_SPEED_OF_SOUND = 116) (not tracked by git)

How This Was Generated

git submodule update --remote
git -C lib/ping-protocol checkout fix/omniscan450-speed-of-sound
python generate/generate-python.py --output-dir brping