Update syncthing to version v1.29.4

[al-lac]

🤖 This is an automated pull request to update syncthing to version v1.29.4. This PR must be reviewed and tested before merging.

Auto-generated update considerations:

• No significant changes or considerations for Docker or Umbrel users in this release

Original GitHub release notes

[github-actions[bot]]

🎉   Linting finished with no errors or warnings   🎉

Thank you for your submission! This is an automated linter that checks for common issues in pull requests to the Umbrel App Store.

Please review the linting results below and make any necessary changes to your submission.

Linting Results

Severity	File	Description
ℹ️	syncthing/docker-compose.yml	External port mapping "22000:22000/tcp": Port mappings may be unnecessary for the app to function correctly. Docker's internal DNS resolves container names to IP addresses within the same network. External access to the web interface is handled by the app_proxy container. Port mappings are only needed if external access is required to a port not proxied by the app_proxy, or if an app needs to expose multiple ports for its functionality (e.g., DHCP, DNS, P2P, etc.).
ℹ️	syncthing/docker-compose.yml	External port mapping "22000:22000/udp": Port mappings may be unnecessary for the app to function correctly. Docker's internal DNS resolves container names to IP addresses within the same network. External access to the web interface is handled by the app_proxy container. Port mappings are only needed if external access is required to a port not proxied by the app_proxy, or if an app needs to expose multiple ports for its functionality (e.g., DHCP, DNS, P2P, etc.).

Legend

Symbol	Description
❌	Error: This must be resolved before this PR can be merged.
⚠️	Warning: This is highly encouraged to be resolved, but is not strictly mandatory.
ℹ️	Info: This is just for your information.

[al-lac]

🤖 This is an automated summary of installation tests for syncthing:

• ✅ App successfully installed in umbrel-dev instance
• ✅ App successfully listed in umbrel.yaml
• ✅ App UI successfully returns a 200 status code

This PR must still be reviewed and tested before merging.

[al-lac]

Tested update on Umbrel Home.