lint: Clear a pair of spellcheck warnings, on `isNaN`.
lint: Clear a pair of spellcheck warnings, on `isNaN`.

The newly-imported redux-persist-migrate code uses `Number.isNaN`,
and that provokes this warning:

  You have a misspelled word: na on Identifier

Sadly neither `isnan` nor the actual name, `isNaN`, seem to help in
skipWords; it must be checking that only after it's already decided to
split the word on caps.

vishwesh3/zulip-mobile,vishwesh3/zulip-mobile,vishwesh3/zulip-mobile,vishwesh3/zulip-mobile