Fix malformed GTK-Doc comment blocks: remove repeated comment blocks.

Fix malformed GTK-Doc comment blocks: remove repeated comment blocks.

gio/gproxyresolver.h: GProxyResolver already documented in gio/giotypes.h
gio/gtlsbackend.h: GTlsBackend already documented in gio/gtlsbackend.c
gio/gtlsclientconnection.h: GTlsClientConnection already documented in gio/gtlsclientconnection.c
gio/gtlsconnection.h: GTlsConnection already documented in gio/gtlsconnection.c
gio/gunixconnection.h: GTcpConnection already documented in gio/giotypes.h
glib/gversion.h: GLIB_CHECK_VERSION already documented in glib/gversion.c

Found these thanks to the improved gobject-introspection
GTK-Doc comment block/annotation parser.
See https://bugzilla.gnome.org/show_bug.cgi?id=672254

https://bugzilla.gnome.org/show_bug.cgi?id=673385