go.mod: bump wireguard-go

This pulls in IP checksum optimization on amd64, see
tailscale/wireguard-go@bb2c8f2.

Updates tailscale/corp#9755

Change-Id: I60e932fc4031703b56eb86a676465c5d02d99236
Signed-off-by: Adrian Dewhurst <adrian@tailscale.com>
This commit is contained in:
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