testing/tailscale: upgrade to 1.8.3
Skipping the wgengine/magicsock test which times out:
ok tailscale.com/wgengine 0.118s
ok tailscale.com/wgengine/bench 0.047s [no tests to run]
ok tailscale.com/wgengine/filter 0.032s
panic: test timed out after 10m0s
...
FAIL tailscale.com/wgengine/magicsock 600.024s
Signed-off-by: Robert Günzler r@gnzler.io