Add psutil to vpython dependencies (used on builder bots)

This is copied from https://chromium-review.googlesource.com/639357

BUG=chromium:761720
NOTRY=True
R=kjellander@webrtc.org
TBR=kwiberg@webrtc.org

Review-Url: https://codereview.webrtc.org/3008063002
Cr-Commit-Position: refs/heads/master@{#19646}
diff --git a/OWNERS b/OWNERS
index 8cc9d35..1efe89f 100644
--- a/OWNERS
+++ b/OWNERS
@@ -7,6 +7,7 @@
 per-file .gitignore=*
 per-file .gn=kjellander@webrtc.org
 per-file *.py=kjellander@webrtc.org
+per-file .vpython=kjellander@webrtc.org
 per-file AUTHORS=*
 per-file BUILD.gn=kjellander@webrtc.org
 per-file DEPS=*