[Bug 1399334] Update pandoc to 1.12.3.3 or 1.12.4 in EPEL7

[Red Hat Bugzilla]

https://bugzilla.redhat.com/show_bug.cgi?id=1399334

--- Comment #1 from Orion Poplawski  ---
Hmm, 1.12.4 may be difficult:

Setup: At least the following dependencies are missing:
aeson ==0.7.*,
highlighting-kate >=0.5.7 && <0.6,
pandoc-types >=1.12.3.3 && <1.13,
tagsoup >=0.13.1 && <0.14,
texmath >=0.6.6.1 && <0.7,
yaml >=0.8.8.2 && <0.9