Fix test failures caused by type hint changes

- Use TYPE_CHECKING guard in recipes.py to prevent typing imports from
  appearing in module namespace (fixes test_recipes_are_documented)
- Update test_convert_help to check for function names with type hints
  in a more flexible way

tests/test_docs.py

@@ -41,9 +41,9 @@ def test_convert_help():
     result = CliRunner().invoke(cli.cli, ["convert", "--help"])
     assert result.exit_code == 0
     for expected in (
-        "r.jsonsplit(value, ",
-        "r.parsedate(value, ",
-        "r.parsedatetime(value, ",
+        "r.jsonsplit(value:",
+        "r.parsedate(value:",
+        "r.parsedatetime(value:",
     ):
         assert expected in result.output