Memory is not cleaned up

[hrkrshnn]

There can be dirty values at the end of the bytes btw.

Need to clean the last memory chunk here.

Take size to be 31 and have all the memory to be dirty. The last bit of the data would be dirty.

Originally posted by @hrkrshnn in https://github.com/transmissions11/solmate/pull/333#discussion_r996169901