LibCrypto: memcmp() all bytes in UnsignedBigInteger::operator==

`length` is only the (trimmed) size of the word vector, so we have to
multiply it with the size of each element to ensure all bytes are
compared.

Fixes #5335.

Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.cpp

@@ -281,7 +281,7 @@ bool UnsignedBigInteger::operator==(const UnsignedBigInteger& other) const
     if (length != other.trimmed_length())
         return false;
 
-    return !__builtin_memcmp(m_words.data(), other.words().data(), length);
+    return !__builtin_memcmp(m_words.data(), other.words().data(), length * (BITS_IN_WORD / 8));
 }
 
 bool UnsignedBigInteger::operator!=(const UnsignedBigInteger& other) const