syncs: fix flaky test by deleting the code it tested (Watch)

Fixes #11766

Change-Id: Id5a875aab23eb1b48a57dc379d0cdd42412fd18b
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
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Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f