Remove alpha status of current_file on chat input

What does this MR do and why?

This MR removes alpha status of current_file on chat input.

The related code_tasks feature has already been rolled out 100% (issue).

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

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Before	After

How to set up and validate locally

1. Check out the MR branch

2. Navigate the GraphiQL playground http://gdk.test:8080/-/graphql-explorer

3. Use the following query and variables.

   mutation chat($question: String!, $currentFileContext: AiCurrentFileInput) {
     aiAction(
       input: {chat: {content: $question, currentFile: $currentFileContext}}
     ) {
       requestId
       errors
       clientMutationId
     }
   }

   {
     "question": "/tests",
     "currentFileContext": {
       "selectedText": "text.split(',')",
       "fileName": "app/models/ci/build.rb",
       "contentAboveCursor": "def split_texts",
       "contentBelowCursor": "end"
     }
   }

4. Confirm there is no errors in the response.