Partially revert "gio: Add missing (array length) annotations"

This reverts commit 80284943

.

Adding (array length=…) to a gchar* parameter causes the GIR file to
contain an array of strings, rather than an array of characters. While
we fix GIR, revert those changes.

Some of the other changes in the file (which have an explicit
(element-type) already) are fine.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

https://bugzilla.gnome.org/show_bug.cgi?id=765063