docs/reference: switch to horizontal ellipsis
docs/reference: switch to horizontal ellipsis

Synchronize the documentation to glib's commit [1] contained in release 2.51.0
for the first time which changed the output format from '[OPTION...]' to
'[OPTION…]' (using the unicode character U+2026 "horizontal ellipsis").

[1] 10c490cdfe3a ("Use Unicode in translatable strings")

Signed-off-by: Ulrich Ölmann <dd989c3d4b9e0c1c162946243f1ca35d034a3035@pengutronix.de>

jluebbe/rauc,rauc/rauc,jluebbe/rauc,ejoerns/rauc,ejoerns/rauc,ejoerns/rauc,rauc/rauc,jluebbe/rauc,rauc/rauc