Add omemo_close function

We call omemo_init() when starting profanity and should have an
omemo_close() at exit.

For now we free the fingerprint autocompleter in there.

Fixes valgrind:
```
==13226== 24 bytes in 1 blocks are definitely lost in loss record 2,855
of 6,958
==13226==    at 0x483677F: malloc (in
/usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==13226==    by 0x48AD39: autocomplete_new (autocomplete.c:57)
==13226==    by 0x4AB89F: omemo_init (omemo.c:127)
==13226==    by 0x42C283: _init (profanity.c:206)
==13226==    by 0x42BFF3: prof_run (profanity.c:98)
==13226==    by 0x4B25E6: main (main.c:172)
```

Regards https://github.com/profanity-im/profanity/issues/1131

1 files changed, 3 insertions, 0 deletions

diff --git a/src/profanity.c b/src/profanity.c
index a9824729..324aa36d 100644
--- a/src/profanity.c
+++ b/src/profanity.c
@@ -242,6 +242,9 @@ _shutdown(void)
 #ifdef HAVE_LIBGPGME
     p_gpg_close();
 #endif
+#ifdef HAVE_OMEMO
+    omemo_close();
+#endif
     chat_log_close();
     theme_close();
     accounts_close();