replace phosek@chromium.org with phosek@google.com in OWNERS

phosek@chromium.org doesn't exist in this host now and that is bit
confusing although phosek@google.com seems to have ownership
implicitly.

Change-Id: I3b8c3ce78eab1f773ab156d9560a5d81a81184ff
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/15221
Reviewed-by: Brett Wilson <brettw@chromium.org>
Reviewed-by: Petr Hosek <phosek@google.com>
Commit-Queue: Takuto Ikuta <tikuta@google.com>
diff --git a/OWNERS b/OWNERS
index 0b140dd..3b888ff 100644
--- a/OWNERS
+++ b/OWNERS
@@ -1,5 +1,5 @@
 brettw@chromium.org
-phosek@chromium.org
+phosek@google.com
 scottmg@chromium.org
 sdefresne@chromium.org
 tikuta@google.com