[VPlan] Remove unused OverrideAllowed arg from getVPValue (NFCI).

Author: fhahn

llvm/lib/Transforms/Vectorize/VPlan.h

@@ -2992,13 +2992,11 @@ class VPlan {
     Value2VPValue[V] = VPV;
   }
 
-  /// Returns the VPValue for \p V. \p OverrideAllowed can be used to disable
-  ///   /// checking whether it is safe to query VPValues using IR Values.
-  VPValue *getVPValue(Value *V, bool OverrideAllowed = false) {
+  /// Returns the VPValue for \p V.
+  VPValue *getVPValue(Value *V) {
     assert(V && "Trying to get the VPValue of a null Value");
     assert(Value2VPValue.count(V) && "Value does not exist in VPlan");
-    assert((Value2VPValueEnabled || OverrideAllowed ||
-            Value2VPValue[V]->isLiveIn()) &&
+    assert((Value2VPValueEnabled || Value2VPValue[V]->isLiveIn()) &&
            "Value2VPValue mapping may be out of date!");
     return Value2VPValue[V];
   }