[NFC] Remove Unused Module Parameter to Conformance Lookup

It's been quite a long time since this unused parameter was introduced.
The intent is to produce the module as a root for the search - that is,
computing the set of conformances visible from that module, not the set
of conformances inside of that module. Callers have since been providing
all manner of module-scoped contexts to it.

Let's just get rid of it. When we want to teach protocol conformance
lookup to do this, we can revert this commit as a starting point and try
again.

lib/AST/ConformanceLookupTable.cpp

@@ -950,7 +950,6 @@ void ConformanceLookupTable::registerProtocolConformance(
 }
 
 bool ConformanceLookupTable::lookupConformance(
-       ModuleDecl *module, 
        NominalTypeDecl *nominal,
        ProtocolDecl *protocol, 
        SmallVectorImpl<ProtocolConformance *> &conformances) {