C#: Remove unused viableImpl predicate

Author: hvitved

csharp/ql/src/semmle/code/csharp/dataflow/internal/DataFlowDispatch.qll

@@ -106,7 +106,7 @@ private module Cached {
 
   /** Gets a viable run-time target for the call `call`. */
   cached
-  DataFlowCallable viableImpl(DataFlowCall call) { result = call.getARuntimeTarget() }
+  DataFlowCallable viableCallable(DataFlowCall call) { result = call.getARuntimeTarget() }
 }
 
 import Cached
@@ -164,8 +164,6 @@ import DispatchImpl
  */
 OutNode getAnOutNode(DataFlowCall call, ReturnKind kind) { call = result.getCall(kind) }
 
-predicate viableCallable = viableImpl/1;
-
 /**
  * A return kind. A return kind describes how a value can be returned
  * from a callable.