Upgrade Mastodon.py to 1.5.1

[fabaff]

Proposed change

Changelog: https://github.com/halcy/Mastodon.py/blob/master/CHANGELOG.rst#v151

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example entry for configuration.yaml:

# Example configuration.yaml
notify:
  - platform: mastodon
    name: mastodon
    access_token: !secret mastodon_access_token
    client_id: !secret mastodon_client_id
    client_secret: !secret mastodon_client_secret

Data for Service call:

{
  "message": "The sun is {% if is_state('sun.sun', 'above_horizon') %}up{% else %}down{% endif %}! A Mastodon.py update for #homeassistant"
}

Result: https://mastodon.social/web/statuses/103883912701961590

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• The code has been formatted using Black (black --fast homeassistant tests)
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

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

• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
• Untested files have been added to .coveragerc.

The integration reached or maintains the following Integration Quality Scale:

• No score or internal
• 🥈 Silver
• 🥇 Gold
• 🏆 Platinum

[MartinHjelmare]

The mystrom_button changes are probably stray changes.