[CIR] Fix error messages when the conversion to MLIR standard dialect…

…s fails. (#1310)

The old error message is wrong, as the `ConvertCIRToMLIRPass` does not
convert to LLVM Dialect but to MLIR standard dialects.

clang/lib/CIR/Lowering/ThroughMLIR/LowerCIRToMLIR.cpp

@@ -1505,11 +1505,12 @@ mlir::ModuleOp lowerFromCIRToMLIR(mlir::ModuleOp theModule,
   auto result = !mlir::failed(pm.run(theModule));
   if (!result)
     report_fatal_error(
-        "The pass manager failed to lower CIR to LLVMIR dialect!");
+        "The pass manager failed to lower CIR to MLIR standard dialects!");
 
   // Now that we ran all the lowering passes, verify the final output.
   if (theModule.verify().failed())
-    report_fatal_error("Verification of the final LLVMIR dialect failed!");
+    report_fatal_error(
+        "Verification of the final MLIR in standard dialects failed!");
 
   return theModule;
 }