Remove some unused functions from the test harness

This was from before `string` was a thing - `_quote` would be better
done as `string escape` and `_echo_var` would be `set --show`.

tests/interactive.config

@@ -18,29 +18,6 @@ set -g fish_greeting ''
 function fish_title
 end
 
-function _quote
-    echo \'(echo $argv[1] | sed -e 's/\'/\\\\\'/g')\'
-end
-
-function _echo_var --no-scope-shadowing -d '_echo_var varname [guardval]'
-    if set -q argv[2]; echo "@GUARD:$argv[2]@"; end
-    set -l var $argv[1]
-    switch (count $$var)
-    case 0
-        echo "\$$var has no value"
-    case 1
-        _quote $$var | read -l x
-        echo "\$$var: $x"
-    case \*
-        echo "\$$var:"
-        for i in (seq (count $$var))
-            _quote $$var[1][$i] | read -l x
-            echo "$i: $x"
-        end
-    end
-    if set -q argv[2]; echo "@/GUARD:$argv[2]@"; end
-end
-
 function _marker -d '_marker string - prints @MARKER:$string@'
     echo "@MARKER:$argv[1]@"
 end