Refactor attribute filtering in PlexObject class

[Dr-Blank]

Description

ref: https://github.com/pkkid/python-plexapi/pull/1302#discussion_r1452938774

The changes optimize the code by using the filter function instead of a list comprehension.

Type of change

Please delete options that are not relevant.

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have added or updated the docstring for new or existing methods
• [x] I have added tests when applicable