binarystore: Don't store max_size

It never actually gets used when it is read, it is always immediately
discarded.

Change-Id: Ib4c6c4ee746a77f0b8704e5d4cf26d78415b9b16
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/proto/binaryblob.proto b/proto/binaryblob.proto
index ceb7735..e4b9b8b 100644
--- a/proto/binaryblob.proto
+++ b/proto/binaryblob.proto
@@ -11,5 +11,6 @@
 message BinaryBlobBase {
     optional string blob_base_id = 1; // Common parent path of contained blobs
     repeated BinaryBlob blobs = 2;
-    optional uint32 max_size_bytes = 3;
+    reserved "max_size_bytes";
+    reserved 3;
 }