Correct format string specifier to match number of parameters (#6266)

toolchain/check/import_ref.cpp

@@ -60,7 +60,7 @@ static auto SetSpecialImportIR(Context& context, SemIR::ImportIR import_ir,
     ir_id = context.import_irs().Add(import_ir);
   }
   CARBON_CHECK(ir_id == expected_import_ir_id,
-               "Actual ImportIRId ($0) != Expected ImportIRId ({1})", ir_id,
+               "Actual ImportIRId ({0}) != Expected ImportIRId ({1})", ir_id,
                expected_import_ir_id);
 }