BACKPORT: kselftests: Add owners

Add Betty and Joe to the OWNERS file.

Test: N/A
Signed-off-by: Edward Liaw <edliaw@google.com>
(cherry picked from https://android-review.googlesource.com/q/commit:7b08a946d2d4ec9cf0da625baa809252075772d9)
[edliaw: resolve merge conflicts with aosp master by removing smuckle, trong and adding drosen, edliaw, willmcvicker]
Merged-In: Ie413fabb8984f05e5c7dc29201115d043eb08a1a
Change-Id: Ie413fabb8984f05e5c7dc29201115d043eb08a1a