net/libzmq4: Remove spurious distinfo entry

Leftover while attempting to use PATCHFILES and PATCH_DIST_STRIP with a local
(not remote) source instead of a files/patch-* file, so one could take verbatim
diffs from GitHub commits/PR's which contain a/ b/ path prefixes, without
having to modify them manually.

PR: 230575
Reported by: ohauer
X-MFH-With: r491260
MFH: 2019Q1