context: move human readable note to stderr (#636)

The NOTE shown when an explicit login isn't provided is output on Stdout
instead of Stderr. This messes up the output of any commands when piping
them to a tool such as `yq`. Move this human readable information to
Stderr so it doesn't break any automated parsing.

Reviewed-on: https://gitea.com/gitea/tea/pulls/636
Co-authored-by: Jake Hillion <jake@hillion.co.uk>
Co-committed-by: Jake Hillion <jake@hillion.co.uk>

modules/context/context.go

@@ -142,7 +142,7 @@ and then run your command again.`)
 			}
 			os.Exit(1)
 		}
-		fmt.Printf("NOTE: no gitea login detected, falling back to login '%s'\n", c.Login.Name)
+		fmt.Fprintf(os.Stderr, "NOTE: no gitea login detected, falling back to login '%s'\n", c.Login.Name)
 	}
 
 	// parse reposlug (owner falling back to login owner if reposlug contains only repo name)