Revert "Add the Sec-CH-UA-Form-Factor header"

This reverts commit 3aa4fb98a44d997de209f76353f4a40c61a441a8.

Reason for revert: Causing test failures in ClientHints https://bugs.chromium.org/p/chromium/issues/detail?id=1456453

Original change's description:
> Add the Sec-CH-UA-Form-Factor header
>
> As described in https://wicg.github.io/ua-client-hints/#sec-ch-ua-form-factor
>
> This is protected by the ClientHintsFormFactor feature flag, which is
> disabled by default, so the CL introduces no new behavior. There are
> still several open questions about the header, but this initial
> implementation should make a suitable starting point regardless of how
> those are decided.
>
> This does _not_:
>  * Add the hint to devtools (this can wait until more questions are answered).
>
> Bug: 1442283
> Change-Id: I964200563ad1f3dea3a8a7a59afc03b5d23f9cf3
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4558705
> Reviewed-by: Ken Buchanan <kenrb@chromium.org>
> Reviewed-by: Arthur Sonzogni <arthursonzogni@chromium.org>
> Reviewed-by: Yoav Weiss <yoavweiss@chromium.org>
> Commit-Queue: Dustin Mitchell <djmitche@chromium.org>
> Reviewed-by: Ari Chivukula <arichiv@chromium.org>
> Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
> Reviewed-by: Brendon Tiszka <tiszka@chromium.org>
> Reviewed-by: Victor Tan <victortan@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1160067}

Bug: 1442283
Change-Id: Idba5177bfdc46c89c5625663677f73c9d23f75cb
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4628153
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: Hailey Wang <haileywang@google.com>
Owners-Override: Hailey Wang <haileywang@google.com>
Commit-Queue: Hailey Wang <haileywang@google.com>
Cr-Commit-Position: refs/heads/main@{#1160180}