Fix bad namespacer

Author: andykaylor

clang/lib/CIR/CodeGen/CIRGenFunction.cpp

@@ -216,7 +216,7 @@ void CIRGenFunction::emitAndUpdateRetAlloca(QualType type, mlir::Location loc,
 void CIRGenFunction::declare(mlir::Value addrVal, const Decl *var, QualType ty,
                              mlir::Location loc, CharUnits alignment,
                              bool isParam) {
-  assert(mlir::isa<NamedDecl>(var) && "Needs a named decl");
+  assert(isa<NamedDecl>(var) && "Needs a named decl");
   assert(!cir::MissingFeatures::cgfSymbolTable());
 
   auto allocaOp = cast<cir::AllocaOp>(addrVal.getDefiningOp());