Problem:
If there are 2 language servers with different trigger chars (`-` and
`>`), and a keymap inputs both simultaneously (`->`), then `>` doesn't
trigger. We get completion items from server1 only.
This happens because the `completion_timer` for the `-` trigger is still
pending.
Solution:
If the next character arrived enough quickly (< 25 ms), replace the
existing deferred autotrigger with a new one that matches this later
character.
(cherry picked from commit e69b81ad94)
556d8d0002