.github: double the timeout for go vet in CI

The job is consistently failing on main when it hits the 5 minute
timeout; let's double it to get useful results.

Updates #cleanup

Change-Id: Iaff2f95d4944929e6832273c94d628f376e2d30e
Signed-off-by: Alex Chan <alexc@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