enchant2: upgrade 2.3.4 -> 2.5.0

enchant2: upgrade 2.3.4 -> 2.5.0

Changelog:
=========
  * A new dictionary method remove_from_session() allows providers to stay
    in sync with Enchant's personal wordlist, by removing as well as adding
    words in the spelling session.
  * The public API enchant_dict_store_replacement() is deprecated, and no
    longer does anything. It only previously had an effect with the Aspell
    provider.
  * The APIs enchant_dict_add() and enchant_dict_remove() also respectively
    add the word to the session or remove it.

Signed-off-by: Wang Mingyu <wangmy@fujitsu.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>