CLN: Some code cleanups in pandas/_libs/parsers.pyx
There are __a lot__ of cdef unused variables in ```pandas/_libs/parsers.pyx``` this PR is covering *some* of the unused variables.

@MomIsBestFriend can you merge master? ~~can you merge master once again, we lost azure coverage; ping on green.~~ /azp run <samp>
Azure Pipelines successfully started running 1 pipeline(s).<br>

</samp> > /azp run

That's very cool, didn't know it's possible. Great thanks @MomIsBestFriend  nice