AK: Fix compile error when using div_mod_internal<513, 256, true>

Author: https://github.com/msvisser
Commit: https://github.com/SerenityOS/serenity/commit/51fe8f820f
Pull-request: https://github.com/SerenityOS/serenity/pull/21949
Reviewed-by: https://github.com/DanShaders
Reviewed-by: https://github.com/alimpfard

AK/UFixedBigIntDivision.h

@@ -39,7 +39,7 @@ constexpr void div_mod_internal(
     if (dividend_len < divisor_len) { // dividend < divisor
         StorageOperations::set(0, quotient);
         if constexpr (restore_remainder)
-            remainder = operand1;
+            StorageOperations::copy(operand1, remainder);
         return;
     }