docs(shlvl): fix repeat example (#6825)

* docs(shlvl): fix repeat example

`$shlvl` needs to be removed from `format` to have a prompt like `❯❯❯`

* docs(shlvl): remove redundant `threshold = 0` in repeat example

docs/config/README.md

@@ -4373,11 +4373,10 @@ status code and preceding characters are provided by `shlvl`.
 
 [shlvl]
 disabled = false
-format = '[$symbol$shlvl]($style)'
+format = '[$symbol]($style)'
 repeat = true
 symbol = '❯'
 repeat_offset = 1
-threshold = 0
 ```
 
 ## Singularity