get rid of already-merged prop221 changes file

changes/prop221

@@ -1,6 +0,0 @@
-  o Minor features:
-    - Stop sending the CREATE_FAST cells by default; instead, use a
-      parameter in the consensus to decide whether to use
-      CREATE_FAST. This can improve security on connections where
-      Tor's circuit handshake is stronger than the available TLS
-      connection security levels. Implements proposal 221.