AST: Remove hack-around for getInterfaceType() on ParamDecl returning InOutType

Most callers did not want the InOutType here, and checked
the ParamDecl's flags instead.

lib/SIL/AbstractionPattern.cpp

@@ -73,7 +73,6 @@ AbstractionPattern TypeConverter::getAbstractionPattern(VarDecl *var) {
     genericSig = sig->getCanonicalSignature();
 
   CanType swiftType = var->getInterfaceType()
-                         ->getInOutObjectType()
                          ->getCanonicalType();
 
   if (auto clangDecl = var->getClangDecl()) {