Statsd atoms: restrict OEM fields 100000-199999

The current wording seems to suggest allocating an infinite number of
fields, which is not future-proof.

Bug: 72866543
Test: N/A
Change-Id: I88732ea8695521a39f20524348547cfe50cbf776

cmds/statsd/src/atoms.proto

@@ -152,8 +152,9 @@ message Atom {
         Temperature temperature = 10021;
     }
 
-    // DO NOT USE field numbers above 100,000 in AOSP. Field numbers above
-    // 100,000 are reserved for non-AOSP (e.g. OEMs) to use.
+    // DO NOT USE field numbers above 100,000 in AOSP.
+    // Field numbers 100,000 - 199,999 are reserved for non-AOSP (e.g. OEMs) to use.
+    // Field numbers 200,000 and above are reserved for future use; do not use them at all.
 }
 
 /**