Fix _toString comment typo

[KamaDeFi]

Question: why does the memory pointer have to be 32-byte aligned? I ran the code reserving exactly 78+32 bytes str := add(mload(0x40), 0x6C), and the execution of the function cost 3 less gas.

[Vectorized]

It must be aligned, or else other code that assumes a 32 byte alignment will break.