Fix -t flag help text to reflect it accepts any goal

The -t flag is not limited to arity 0 predicates - it accepts any
goal including goals with arguments (e.g., -t 'halt(1)'). Updated
the help text to remove the incorrect "(arity 0 predicate)" constraint.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/toplevel.pl

@@ -110,7 +110,7 @@ print_help :-
     write('   -g, --goal GOAL        '),
     write('Run the query GOAL'), nl,
     write('   -t GOAL                '),
-    write('Use GOAL as custom toplevel (arity 0 predicate)'), nl,
+    write('Use GOAL as custom toplevel'), nl,
     write('   -f                     '),
     write('Fast startup. Do not load initialization file (~/.scryerrc)'), nl,
     write('   --no-add-history       '),