pf tests: Fix accidental duplication of content

Some files got their contented duplicated in r345409. Some mistakes where
fixed in r345430. The only file that was left with a duplicated content was
CVE-2019-5598.py.

Reviewed by: kp
Approved by: src (kp)
Differential Revision: https://reviews.freebsd.org/D21267

(cherry picked from commit 03d8a4b7d39af6da7ceaaf07211cf0fde1e623ed)