GKeyFile: fix annotation of g_key_file_load_from_data

(array) without (element-type) means "array of the same type as
the C type", so gchar* with (array) is interpreted as an array of
strings. Since GKeyFiles must be UTF-8 encoded anyway, just
annotate it as a string.

https://bugzilla.gnome.org/show_bug.cgi?id=658484

glib/gkeyfile.c

@@ -862,8 +862,8 @@ 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
- * @length: the length of @data in bytes
+ * @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
  *