revert D1471958. ParseError is not intended to be caught

revert D1471958. ParseError is not intended to be caught

Summary:
a couple of files were catching this exception and included the .cpp file :O. So we moved
to .h before realizing this was not intended to be caught. reverting the move to .h. codemod will follow.

Test Plan: fbmake -r folly && fbmake && fbmake runtests

Reviewed By: delong.j@fb.com

Subscribers: trunkagent, doug, seanc, folly-diffs@, yfeldblum

FB internal diff: D1854301

Tasks: 6245781

Signature: t1:1854301:1424375745:7e226196315fac99835752896cc5e549e91df2da