filetype/mercurial: Fix file name regex

The regex for detecting Mercurial's file types was too strict and
didn't catch commit messages.

Relax it to make it detect the commit files properly.

rc/filetype/mercurial.kak

@@ -4,7 +4,7 @@
 # Detection
 # ‾‾‾‾‾‾‾‾‾
 
-hook global BufCreate .*hg-editor-\w+\.txt$ %{
+hook global BufCreate .*hg-editor-.*\.txt$ %{
     set-option buffer filetype hg-commit
 }