Suggestion: drop default system prompt feature

[nahoj]

Hi. In November I requested a feature to set a common system prompt for all the models provided by the Google Gemini pipe and I thank you again for it. Since then I created a simple filter to do the same thing based on tags, and I saw a similar one on https://openwebui.com/ filtering on model ID instead.

So I personally don't use the pipe's feature anymore. I think you could remove it from the pipe if you wanted, since anyone who wants this can use one of the filters for it. Cheers.