Update PlexAPI to f-strings

[JonnyWong16]

Description

Updates all string formatting to use f-strings.

Used flynt to convert f-strings. https://github.com/ikamensh/flynt

Type of change

Please delete options that are not relevant.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

Checklist:

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