Add "# COMPONENT" to system_api OWNERS file

See https://tinyurl.com/yxau5sc4 for context.

Bug: 977050
No-Try: true
Change-Id: I7f61449898a323bc8e8e960527d0e5fcfaa71d1f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/1845878
Tested-by: Eric Foo <efoo@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/system_api/OWNERS b/system_api/OWNERS
index 03f0a21..daa38e6 100644
--- a/system_api/OWNERS
+++ b/system_api/OWNERS
@@ -4,3 +4,5 @@
 # about the component whose constants you're changing.
 vapier@chromium.org
 ejcaruso@chromium.org
+
+# COMPONENT: OS>Systems