diffs: remove unused argument enable_comments and class no-comment enable_comments was only used to set/not-set the 'no-comment' CSS class. While this class was emitted, no CSS rule nor any JavaScript logic was actually using it. Last real usage of that class was removed with commit e87baa8f1c5bd2488aefc23b95c0db3a04bc8431. Cleanup the code by not emitting 'no-comment' and remove the 'enable_comments' flag.

[tox]
minversion = 1.8
envlist = py27-pytest

[testenv]
setenv =
    PYTHONHASHSEED = 0
deps =
    -r{toxinidir}/dev_requirements.txt
    python-ldap
    python-pam
commands =
    pytest: py.test {posargs}