Remove system/core/METADATA

This directory doesn't contain third-party code and it doesn't need a METADATA file.

Bug: 380376695
Test: CIs
Change-Id: Ie197786da09304476fb002b178c2a77d424f5a53
diff --git a/METADATA b/METADATA
deleted file mode 100644
index d97975c..0000000
--- a/METADATA
+++ /dev/null
@@ -1,3 +0,0 @@
-third_party {
-  license_type: NOTICE
-}