fix: remove python version constraint for typing_extensions to prevent import errors for >=3.8

[ttaschke]

Importing pyflp after installation with pip install -e . on newer Python version (>=3.8) throws a ModuleNotFoundError, because typing_extensions is imported, but not installed for newer Python versions.

Example:

Python 3.10.7 (main, Sep  7 2022, 22:40:42) [GCC 11.2.1 20220219] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import pyflp
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/python_project/pyflp/__init__.py", line 53, in <module>
    from .project import VALID_PPQS, FileFormat, Project, ProjectID
  File "/python_project/pyflp/project.py", line 31, in <module>
    from typing_extensions import Unpack
ModuleNotFoundError: No module named 'typing_extensions'

After applying this fix importing pyflp works without throwing an error.
(Parsing example is just to show that pyflp was imported correctly, the error thrown is unrelated to the typing_extension problem)

Python 3.10.7 (main, Sep  7 2022, 22:40:42) [GCC 11.2.1 20220219] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import pyflp
>>> project = pyflp.parse("../test_data/melody.flp")
/python_project/pyflp/pyflp/__init__.py:151: RuntimeWarning: Event 212 not parsed entirely; parsed 18, found 52 bytes
  events.append(event_type(id, value))
/python_project/pyflp/pyflp/__init__.py:151: RuntimeWarning: Event 215 not parsed entirely; parsed 158, found 168 bytes
  events.append(event_type(id, value))

[demberto]

Hmm yea, I kinda just overlooked the constraint. Thanks.

[demberto]

@allcontributors please add @ttaschke for code

[allcontributors]

@demberto

I've updated the pull request to add @ttaschke! 🎉