Do not call update() in constructor

[fabaff]

Description:

• Do not call update() in constructor
• Update ordering
• Update docstrings

Example entry for configuration.yaml (if applicable):

sensor:
  - platform: pocketcasts
    username: !secret pc_username
    password: !secret pc_password

Checklist:

If the code communicates with devices, web services, or third-party tools:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass

[mention-bot]

@fabaff, thanks for your PR! By analyzing the history of the files in this pull request, we identified @molobrakos and @andrey-git to be potential reviewers.