doc: remove GNU troff workaround

In 2007 the docbook project made the mistake of converting ' to \' for man pages [1]. It's a problem because groff interprets \' as acute accent which is rendered as ' in ASCII, but as ´ in utf-8. This started a cascade of bug reports in git [2], debian [3], Arch Linux [4], docbook itself [5], and probably many others. A solution was to use the correct groff character: \(aq, which is always rendered as ', but the problem is that such character doesn't work in other troff programs. A portable solution required the use of a conditional character that is \(aq in groff, but ' in all others: .ie \n(.g .ds Aq \(aq .el .ds Aq ' The proper solution took time to be implemented in docbook, but in 2010 they did it [6]. So the docbook man page stylesheets were broken from 1.73 to 1.76. Unfortunately by that point many workarounds already existed. In the case of git, GNU_ROFF was introduced, and in the case of Arch Linux a mapping from \' to ' was added to groff's man.local. Other distributions might have done the same, or similar workarounds. Since 2010 there is no need for this workaround, which is fixed elsewhere, not just in docbook, but other layers as well. Let's remove it. [1] https://github.com/docbook/xslt10-stylesheets/commit/ea2a0bac56c56eec1892ac3d9254dca89f7c5746 [2] https://lore.kernel.org/git/20091012102926.GA3937@debian.b2j/ [3] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=507673#65 [4] https://bugs.archlinux.org/task/9643 [5] https://sourceforge.net/p/docbook/bugs/1022/ [6] https://github.com/docbook/xslt10-stylesheets/commit/fb553434265906ed81edc6d5f533d0b08d200046 Inspired-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com> Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>