[Files App] Fix default preferences mismatch on base::contains

Previously, when searching for default preferences options among our entry file tasks, some TaskDescriptors went undetected when calling
base:contains(). This was because the previously defined TaskDescriptor "<" operator caused comparison inconsistencies between how we sorted TaskDescriptors while they got added to a std::set container and how we detected them in our base::contains() call in ChooseAndSetDefault.

Bug: 1340095
Change-Id: If4ad71aaf47de64aa5cb9d372b79041f3a771134
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3763546
Reviewed-by: Tim Sergeant <tsergeant@chromium.org>
Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Vivian Pao <vpao@google.com>
Cr-Commit-Position: refs/heads/main@{#1026087}