net/http: TestIdentityResponse failure on windows-amd64-2008

[bcmills]

--- FAIL: TestIdentityResponse (21.01s)
    serve_test.go:1054: error dialing: dial tcp 127.0.0.1:50680: connectex: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.
FAIL
FAIL	net/http	25.184s

greplogs -l -e 'FAIL: TestIdentityResponse' --since=2021-01-01
2022-05-12T00:24:40-a2d1207/windows-amd64-2008

windows/amd64 is a first class port, but since there is only one of these failures in the past ~2 years I'm leaving this on the backlog to collect more information about which platforms may be affected. (See previously #38112.)

(CC @NeilDL)