Revert "[Partitioned Popins] Track is_partitioned_popin_"

This reverts commit 4fe180657934e7afa8d8e3f0383709f83fcbd4fc.

Reason for revert:
external/wpt/partitioned-popins/partitioned-popins.permission-all.tentative.sub.https.window.html
started crashing after this CL.

Looks like we're hitting the DCHECK added in line 871. See first
failing build here:
https://ci.chromium.org/ui/p/chromium/builders/ci/mac11-arm64-rel-tests/47946/test-results?sortby=&groupby=

Original change's description:
> [Partitioned Popins] Track is_partitioned_popin_
>
> We should track whether a window is a partitioned popin independent of
> if an opener is set as it's possible for the opener RFH to go away
> before the popin is closed, but this should not mean the window is no
> longer considered a popin.
>
> A DCHECK was added to detect if IsPartitionedPopin checks are done in
> this window as we should still prevent it if possible.
>
> Explainer: https://explainers-by-googlers.github.io/partitioned-popins/
> I2P: https://groups.google.com/a/chromium.org/g/blink-dev/c/ApU_zUmpQ2g/
>
> Bug: 340606651
> Change-Id: I8e09639084d911bc956ca675dc0f0fcb41126438
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5973438
> Auto-Submit: Ari Chivukula <arichiv@chromium.org>
> Reviewed-by: Sandor «Alex» Major <sandormajor@google.com>
> Reviewed-by: Nasko Oskov <nasko@chromium.org>
> Commit-Queue: Ari Chivukula <arichiv@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1375997}

Bug: 340606651
Change-Id: I71a193f993ad3ef106c832bef61f0a0056b7a390
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5981452
Owners-Override: Giovanni Ortuno Urquidi <ortuno@chromium.org>
Commit-Queue: Giovanni Ortuno Urquidi <ortuno@chromium.org>
Auto-Submit: Giovanni Ortuno Urquidi <ortuno@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1376128}