meson: do not replace datadir for bash completion
meson: do not replace datadir for bash completion

With earlier commit we changed from redefine/replace datadir with ours.
Although that resulted in the completion being installed to the wrong
place /usr/usr/share/bash-completion/completions/

A proper solution is to not redefine/replace the variable at all. Since
doing so will result in the file(s) being installed where bash cannot
find them.

Fixes: acf1333 ("Initial meson build system")
Closes: https://gitlab.freedesktop.org/mesa/waffle/-/issues/59
Signed-off-by: Emil Velikov <f20878473f414da183da19ee25c8722cc1d711e4@collabora.com>

waffle-gl/waffle,waffle-gl/waffle,waffle-gl/waffle,waffle-gl/waffle