fix delete chat message button

[priyashpatil]

Description

The purpose of having delete button was to delete any previous chat history to reduce the input length to LLM.

• [x] fix out of index issue on delete chat message.
• [x] fix deleting related chat prompt.
• [x] hide delete on last response.

Closes #2065

Checklist

• [x] The base branch of this PR is dev, rather than main
• [x] The relevant docs, if any, have been updated or created