[skcq] Allow tasks.json to be modified by non-committers
[skcq] Allow tasks.json to be modified by non-committers

It is a common file to modify and only committers are
going to approve the change.

Bug: skia:12053
Change-Id: I18239153798a1f2f8469e85132157324a81ba48e
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/431616
Reviewed-by: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>
Commit-Queue: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot