fix(sql): fix autocomplete when omni is used as a blink.cmp source (#5652)

## Description

I was trying the `omni` source with `blink.cmp` and I had an error which
you can read more about in this `nvim-compe` issue:
https://github.com/hrsh7th/nvim-compe/issues/286 but the message keeps
showing up after setting that to `syntax` so I mark the default plugin
as loaded, and it works as expected, I think there are more items
returned but I cannot confirm that :).

## Checklist

- [x] I've read the
[CONTRIBUTING](https://github.com/LazyVim/LazyVim/blob/main/CONTRIBUTING.md)
guidelines.

lua/lazyvim/plugins/extras/lang/sql.lua

@@ -28,6 +28,11 @@ end
 
 local sql_ft = { "sql", "mysql", "plsql" }
 
+-- disable nvim default `sql_completion` plugin to be compatible with blink.cmp's omni
+-- while still showing some keywords from the syntax autocomplete sources
+vim.g.omni_sql_default_compl_type = "syntax"
+vim.g.loaded_sql_completion = true
+
 return {
   recommended = function()
     return LazyVim.extras.wants({