Fix typo: s.mgth() -> s.size() in 3234.Count-the-Number-of-Substrings-With-Dominant-Ones

[chl131]

Fix typo: s.mgth() -> s.size() in 3234.Count-the-Number-of-Substrings-With-Dominant-Ones

Also, we don't need max() on line 24:

ret += extra+1;

because the if statement:

if (right[j-1] + have >= count*count)

already ensures the variable extra is non-negative.