[sil] Change SILDefaultWitnessTable verification to use verificationEnabled instead of #ifndef NDEBUG to match the rest of the SILVerifier.

I think this was just an oversight. There is really no reason that this should
not match the rest of the SILVerifier w here we have moved from using #ifndef
NDEBUG to verificationEnabled checking.

Author: gottesmm

lib/SIL/Verifier/SILVerifier.cpp

@@ -7688,7 +7688,9 @@ void SILWitnessTable::verify(const SILModule &M) const {
 
 /// Verify that a default witness table follows invariants.
 void SILDefaultWitnessTable::verify(const SILModule &mod) const {
-#ifndef NDEBUG
+  if (!verificationEnabled(mod))
+    return;
+
   for (const Entry &entry : getEntries()) {
     // FIXME: associated type witnesses.
     if (!entry.isValid() || entry.getKind() != SILWitnessTable::Method)
@@ -7709,7 +7711,6 @@ void SILDefaultWitnessTable::verify(const SILModule &mod) const {
                SILFunctionTypeRepresentation::WitnessMethod &&
            "Default witnesses must have witness_method representation.");
   }
-#endif
 }
 
 /// Verify that a global variable follows invariants.