Revert "[iOS] Update field trial config and about_flags for CPE promo"

This reverts commit b358145a.

Reason for revert: This is causing EG tests to fail. Example:
https://ci.chromium.org/ui/p/chrome/builders/ci/iphone-device/37154/overview

Original change's description:
> [iOS] Update field trial config and about_flags for CPE promo
>
> This change:
> * Updates the testing_field_trial_config.json and about_flags
>   to add a new experiment/feature flag param. This param will allow
>   all of the promo's triggers to be enabled at once.
>
> * Checks for the CPE promo feature in the password manager tests.
>   The addition to the fieldtrial config enables the copy password
>   arm by default, which will cause the promo to appear in some
>   tests.
>
> This CL will be followed by an update to the CPE promo finch config.
>
> Bug: None
> Change-Id: I4c5b9a6f517f44ff0b977a401c1582f0cae27079
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4547450


> Reviewed-by: Tommy Martino <tmartino@chromium.org>
> Commit-Queue: Hira Mahmood <hiramahmood@google.com>
> Cr-Commit-Position: refs/heads/main@{#1147895}

Bug: None
Change-Id: I6db01359b8fc5c23a85fbdb6a847d6dc926c2906
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4559205


Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Ginny Huang <ginnyhuang@chromium.org>
Commit-Queue: Scott Yoder <scottyoder@google.com>
Owners-Override: Scott Yoder <scottyoder@google.com>
Cr-Commit-Position: refs/heads/main@{#1148181}