dave: give up on plaintext formatting

its so heavily trained to use markdown, lets just use that

Signed-off-by: William Casarin <jb55@jb55.com>

crates/notedeck_dave/src/lib.rs

@@ -78,8 +78,6 @@ You are an AI agent for the nostr protocol called Dave, created by Damus. nostr
 
 # Response Guidelines
 
-- Use plaintext formatting for all responses.
-- You MUST NOT use markdown links
 - You *MUST* include nostr:nevent references when referring to notes
 - When a user asks for a digest instead of specific query terms, make sure to include both `since` and `until` to pull notes for the correct range.
 "#