[bindings] Replace deprecated allow-none with optional and nullable

src/hb-blob.cc

@@ -82,8 +82,8 @@ _hb_blob_destroy_user_data (hb_blob_t *blob)
  * @data: (array length=length) (element-type uint8_t) (closure user_data) (destroy destroy) (scope notified) (transfer none): Pointer to blob data.
  * @length: Length of @data in bytes.
  * @mode: Memory mode for @data.
- * @user_data: (allow-none): Data parameter to pass to @destroy.
- * @destroy: (allow-none): Callback to call when @data is not needed anymore.
+ * @user_data: (nullable): Data parameter to pass to @destroy.
+ * @destroy: (nullable): Callback to call when @data is not needed anymore.
  *
  * Creates a new "blob" object wrapping @data.  The @mode parameter is used
  * to negotiate ownership and lifecycle of @data.

src/hb-shape.cc

@@ -200,7 +200,7 @@ parse_one_feature (const char **pp, const char *end, hb_feature_t *feature)
  * hb_feature_from_string:
  * @str: (array length=len):
  * @len: 
- * @feature: (out) (allow-none):
+ * @feature: (out) (optional):
  *
  * 
  *

src/hb-unicode.cc

@@ -157,7 +157,7 @@ hb_unicode_funcs_get_default (void)
 
 /**
  * hb_unicode_funcs_create: (Xconstructor)
- * @parent: (allow-none):
+ * @parent: (nullable):
  *
  * 
  *