Remove .isolate files from OWNER files

BUG=703799
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel
TBR=brettw

Review-Url: https://codereview.chromium.org/2766403002
Cr-Original-Commit-Position: refs/heads/master@{#458866}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: b2248caa5161d50cf3575be77f27544846ec83bb