fix(which_key): close window on mouse click action (#3053)

* fix(which_key): close window on mouse click action

`nvim_buf_delete` is not allowed during text change or window change.
Window switching with left mouse click was leading to race
condition/error.

* [docgen] Update doc/telescope.txt
skip-checks: true

---------

Co-authored-by: Github Actions <actions@github>
(cherry picked from commit d00d9df48c)

doc/telescope.txt

@@ -3298,6 +3298,8 @@ action_generate.which_key({opts})     *telescope.actions.generate.which_key()*
                                             "TelescopePromptBorder")
         {winblend}               (number)   pseudo-transparency of keymap
                                             hints floating window
+        {zindex}                 (number)   z-index of keymap hints floating
+                                            window (default: 100)