syncthing: Update to 1.7.1

This hotfix release fixes an issue with block validation.

Bugfixes:

    #6827: syncthing 1.6.1 -> 1.7.0 fails on "failed validating data"

v1.7.0

This release performs a database migration to optimize for clusters with
many devices.

Bugfixes:

    #6552: panic: Stop called more than once on ... created by nat.Service
    #6564: Closing an already removed connection causes GUI error message
    #6646: Misleading error message when to be deleted dir contains receive-only changes
    #6653: panic: nil pointer dereference in leveldb.(*DB).isClosed()
    #6654: panic: runtime error: index out of range in processNeeded()
    #6655: panic: nil pointer dereference in checkUpgrade()
    #6679: QUIC listener is not added when default TCP port is unavailable
    #6697: Malformed listen address causes hang on startup
    #6706: Changing a folder in web UI removes introduced-by info

Enhancements:

    #1830: "Folder path missing" when folder path is a junction
    #4703: Suggest setting up auth on initial startup
    #5910: Add Badger database backend for testing and consideration
    #6372: Reduce database size by optimizing version list storage

Other issues:

    #6608: Data race in Windows fs watcher tests
    #6625: TestRequestRemoteRenameChanged is racy/flaky

(nia)