Revert "[iOS]Change AccountMenuCoordinator parent class"

This reverts commit 3777145bdbf63dfb38ff574a94b25cfc2b454843.

Reason for revert:
LUCI Bisection has identified this change as the cause of a test failure. See the analysis: https://ci.chromium.org/ui/p/chromium/bisection/test-analysis/b/6263102594088960

Sample build with failed test: https://ci.chromium.org/b/8716140076041568673
Affected test(s):
[ninja://ios/chrome/test/earl_grey2:ios_chrome_settings_eg2tests_module/ManageSyncSettingsTestCase/testSignOutFromAccountFromAccountMenu](https://ci.chromium.org/ui/test/chromium/ninja:%2F%2Fios%2Fchrome%2Ftest%2Fearl_grey2:ios_chrome_settings_eg2tests_module%2FManageSyncSettingsTestCase%2FtestSignOutFromAccountFromAccountMenu?q=VHash%3A31534deaba62d344)

If this is a false positive, please report it at http://b.corp.google.com/createIssue?component=1199205&description=Analysis%3A+https%3A%2F%2Fci.chromium.org%2Fui%2Fp%2Fchromium%2Fbisection%2Ftest-analysis%2Fb%2F6263102594088960&format=PLAIN&priority=P3&title=Wrongly+blamed+https%3A%2F%2Fchromium-review.googlesource.com%2Fc%2Fchromium%2Fsrc%2F%2B%2F6449972&type=BUG

Original change's description:
> [iOS]Change AccountMenuCoordinator parent class
>
> Before this CL the AccountMenuCoordinator directly implemented
> SigninCoordinator. It used to be necessary due to restriction in the
> AddAccountCoordinator. Now that this restriction is gone, we can
> simplify some part of the code by ensuring that AccountMenuCoordinator
> directly extends ChromeCoordinator.
>
> Bug: 381444097
> Change-Id: Id1a17471d9566372731cd182e6bd3e4cb8996b48
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6449972
> Reviewed-by: Mark Cogan <marq@chromium.org>
> Reviewed-by: Jérôme Lebel <jlebel@chromium.org>
> Auto-Submit: Arthur Milchior <arthurmilchior@chromium.org>
> Commit-Queue: Arthur Milchior <arthurmilchior@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1454033}
>

Bug: 381444097
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: Iab47237decf7c4c6c165d208d782cb8f8df13f3b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6503578
Owners-Override: Justin Cohen <justincohen@chromium.org>
Reviewed-by: Federica Germinario <fedegermi@google.com>
Reviewed-by: Justin Cohen <justincohen@chromium.org>
Commit-Queue: Federica Germinario <fedegermi@google.com>
Cr-Commit-Position: refs/heads/main@{#1454944}