test: move http timeout test to parallel

test-http-client-timeout-option-with-agent no longer checks that the
timeout happens within a certain tolerance so it can be moved to the
parallel test suite.

PR-URL: #22403
Reviewed-By: Ruben Bridgewater <[email protected]>
Reviewed-By: Refael Ackermann <[email protected]>
Reviewed-By: Joyee Cheung <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>

Author: Trott