test: remove blank lines at end of files

In preparation for a lint rule that disallows empty lines at the end of
a file, remove such lines from a number of test files.

Refs: https://github.com/nodejs/node/issues/8918
PR-URL: https://github.com/nodejs/node/pull/8920


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ilkka Myller <ilkka.myller@nodefield.com>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Roman Reiss <me@silverwind.io>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>