fix: add permission checks before fetching messages in reaction events

[feelixs]

Pull Request Type

• Feature addition
• Bugfix
• Documentation update
• Code refactor
• Tests improvement
• CI/CD pipeline enhancement
• Other: [Replace with a description]

Description

Changes

• Updated ReactionEvents._handle_message_reaction_change() to check for correct channel permissions before attempting to fetch a message from Discord.

Related Issues

#1753

Test Scenarios

Test the updated code thru a bot's handling of reaction changes:

• Create a channel in a discord server with your test bot, and disable the bot's "Read Message History" permission in it.
• Add the OS environment variables BOT_TOKEN and BOT_TEST_CHANNEL_ID (the id of your new channel)
• Run tests/test_bot.py
• In test_reaction_events(), you will need to react with the ✅ emoji to the bot's newly sent message.
• The test will work with the updated code, but throws an error 403 missing access with the old code.

Python Compatibility

• I've ensured my code works on Python 3.10.x
• I've ensured my code works on Python 3.11.x

Checklist

• I've run the pre-commit code linter over all edited files
• I've tested my changes on supported Python versions
• I've added tests for my code, if applicable
• I've updated / added documentation, where applicable

[feelixs]

@interactions-py mentioning bc contributing.rst says to :)