fix(docs): clean up non-docstring comments for vimdoc gen

These non-docstring comments can be included into doxygen's brief
description and then appear in the succeeding function documentation.

runtime/lua/vim/shared.lua

@@ -579,7 +579,7 @@ function vim.tbl_isarray(t)
   local count = 0
 
   for k, _ in pairs(t) do
-    --- Check if the number k is an integer
+    -- Check if the number k is an integer
     if type(k) == 'number' and k == math.floor(k) then
       count = count + 1
     else