Remove FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS in DragAndDropLauncherActivity
trampoline launch

Without this removal, we were previously propagating this flag set for
the trampoline DragAndDropLauncherActivity incorrectly to
ChromeTabbedActivity, that was causing it to be missing from Recents
when created via tab tearing.

Bug: 403501855
Change-Id: Ib38c71b3a69f0df6e5bc20def61735eb2bbb19aa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6382258
Reviewed-by: Sirisha Kavuluru <skavuluru@google.com>
Commit-Queue: Aishwarya Rajesh <aishwaryarj@google.com>
Cr-Commit-Position: refs/heads/main@{#1436215}