[feaLib] Fix test failures caused by an earlier bug fix
[feaLib] Fix test failures caused by an earlier bug fix

An earlier change made sure that language tags would always be
four characters in length, even when ending in whitespace.
This made a few test cases in parser_test.py fail. By accident,
I had only run builder_test (instead of all unittest in fonttools)
before committing that change.

googlefonts/fonttools,fonttools/fonttools