Change cmd2 version specification to exact match

[d-steffan]

cmd2>=2.3.0 generated the following error:

Traceback (most recent call last):
  File "/home/user/venv/bin/faraday-cli", line 5, in <module>
    from faraday_cli.shell.main import main
  File "/home/user/venv/lib/python3.12/site-packages/faraday_cli/shell/main.py", line 4, in <module>
    from faraday_cli.shell.shell import FaradayShell
  File "/home/user/venv/lib/python3.12/site-packages/faraday_cli/shell/shell.py", line 15, in <module>
    from cmd2 import (
ImportError: cannot import name 'style' from 'cmd2' (/home/user/venv/lib/python3.12/site-packages/cmd2/__init__.py). Did you mean: 'styles'?

changed to exact version match to be functional at least.