Remove "XSLT" runtime enabled feature

The flag was introduced at
https://crrev.com/eae49e58e1365c1d010cb49b6d2eb87823904fc4 to run
an experiment to disable the feature, but it was more than 5 years ago.
Remove the flag as there seems no activity around it.

Bug: None
Change-Id: I186e804da25138455eef4ca8a66812ff40fb7e29
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1575261
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#653117}
17 files changed