ChangeLog: delete both consensus flavours to un-break nss

The required protocol version check occurs before the consensus flavour
check. So on directory mirrors (and some client configs), alpha users need
to delete both consensus flavours to workaround nss bugs.

Closes ticket 27756.

ChangeLog

@@ -62,7 +62,8 @@ Changes in version 0.3.5.1-alpha - 2018-09-18
 
       If you are experimenting with this option and using an old cached
       consensus, Tor may fail to start. To solve this, delete your
-      "cached-microdesc-consensus" file, and restart Tor.
+      "cached-consensus" and "cached-microdesc-consensus" files,
+      (if present), and restart Tor.
 
   o Major bugfixes (directory authority):
     - Actually check that the address we get from DirAuthority