[depot_tools] Migrate metadata to DIR_METADATA.

Change-Id: I7e07de8746a269a31744f44296921cc9c6566a73
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2597738
Reviewed-by: Andy Perelson <ajp@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Auto-Submit: Edward Lesmes <ehmaldonado@chromium.org>

DIR_METADATA

@@ -0,0 +1,3 @@
+monorail: {
+  component: "Infra>SDK"
+}

OWNERS

@@ -37,5 +37,3 @@ per-file led*=file://LUCI_OWNERS
 per-file luci*=file://LUCI_OWNERS
 per-file vpython*=file://LUCI_OWNERS
 per-file LUCI_OWNERS=file://LUCI_OWNERS
-
-# COMPONENT: Infra>SDK