Fix missing case statement at beginning of specification

Wasn't being displayed on github; adding an empty line prior to the spec
seems to fix this.

bip-0065.mediawiki

@@ -195,6 +195,7 @@ transaction output ''can'' be spent.
 Refer to the reference implementation, reproduced below, for the precise
 semantics and detailed rationale for those semantics.
 
+    
     case OP_NOP2:
     {
         // CHECKLOCKTIMEVERIFY