Remove identifier argument from core probe WillSendRequest

Since the CHECK_EQ in inspector_network_agent.cc:1042
https://source.chromium.org/chromium/chromium/src/+/master:third_party/blink/renderer/core/inspector/inspector_network_agent.cc;drc=3de98e520cea74e1f1bdc8a112bb66a8f2a19541;l=1042
never fired, I assume this refactoring is correct.

Bug: chromium:1072057
Change-Id: I6898a22a6b30342a84f1593a6ed8c8f605969696
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2760178


Reviewed-by: Nate Chapin <japhet@chromium.org>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#865078}