weechat: update wee-slack submodule

diff --git a/weechat/python/wee-slack b/weechat/python/wee-slack
index 7bf0ea6a4eedc0c98152b3b13f1394676a39d4dd..31c7e9acde467b8df8efc319fad1971d387b1361 160000 (submodule)
--- a/weechat/python/wee-slack
+++ b/weechat/python/wee-slack
@@ -1 +1 @@
-Subproject commit 7bf0ea6a4eedc0c98152b3b13f1394676a39d4dd
+Subproject commit 31c7e9acde467b8df8efc319fad1971d387b1361