fix: AttributeError when decoding a function

[leoferaderonugraha]

So, i started using frida yesterday; when i'm trying to explore the manual on the frida tools, i got this error:

  File "C:\Users\xxx\AppData\Local\Python\pythoncore-3.14-64\Lib\site-packages\frida_tools\repl.py", line 532, in _print_help
    signature = self._evaluate_expression("%s.toString()" % obj_to_identify)[1].decode()
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'str' object has no attribute 'decode'. Did you mean: 'encode'?

This PR is an effort to fix that, but in the essence, it would be great to contribute to the documentation part itself.
Since i don't know how the direction of the documentation would be built, it would be great if you could share it with us.

edit: frida version i've been using: 17.6.2