Revert unintential IAPI break for g_key_file_load_from_data()

The old (length) annotation actually wasn't being read.  Changing
it to an array was telling g-i that it was an array of utf8, which
is clearly not true.

We *could* add (element-type guint8), but that would change it to a
byte array, as opposed to the original utf8 version.

Just removing the annotation should bring us back to where we
were, which was fine.

https://bugzilla.gnome.org/show_bug.cgi?id=680310

glib/gkeyfile.c

@@ -861,7 +861,7 @@ g_key_file_load_from_file (GKeyFile       *key_file,
 /**
  * g_key_file_load_from_data:
  * @key_file: an empty #GKeyFile struct
- * @data: (array length=length): key file loaded in memory
+ * @data: key file loaded in memory
  * @length: the length of @data in bytes (or -1 if data is nul-terminated)
  * @flags: flags from #GKeyFileFlags
  * @error: return location for a #GError, or %NULL