refactor: update to py39 typehints and removeprefix

[onerandomusername]

Updates all of the typehints in the project to 3.9 style typehinting. Also fixes a few methods to use removeprefix and removesuffix.

[read-the-docs-community]

Documentation build overview

📚 disnake | 🛠️ Build #29887189 | 📁 Comparing 066286a against latest (26ab16c)

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Show files changed (48 files in total): 📝 48 modified | ➕ 0 added | ➖ 0 deleted

File	Status
index.html	📝 modified
whats_new.html	📝 modified
api/abc.html	📝 modified
api/activities.html	📝 modified
api/app_commands.html	📝 modified
api/app_info.html	📝 modified
api/audit_logs.html	📝 modified
api/automod.html	📝 modified
api/channels.html	📝 modified
api/clients.html	📝 modified
api/components.html	📝 modified
api/emoji.html	📝 modified
api/entitlements.html	📝 modified
api/events.html	📝 modified
api/exceptions.html	📝 modified
api/guild_scheduled_events.html	📝 modified
api/guilds.html	📝 modified
api/integrations.html	📝 modified
api/interactions.html	📝 modified
api/invites.html	📝 modified
api/localization.html	📝 modified
api/members.html	📝 modified
api/messages.html	📝 modified
api/misc.html	📝 modified
api/permissions.html	📝 modified
api/roles.html	📝 modified
api/skus.html	📝 modified
api/soundboard.html	📝 modified
api/stage_instances.html	📝 modified
api/stickers.html	📝 modified
api/subscriptions.html	📝 modified
api/ui.html	📝 modified
api/users.html	📝 modified
api/utilities.html	📝 modified
api/voice.html	📝 modified
api/webhooks.html	📝 modified
api/widgets.html	📝 modified
ext/tasks/index.html	📝 modified
ext/commands/api/app_commands.html	📝 modified
ext/commands/api/bots.html	📝 modified
ext/commands/api/checks.html	📝 modified
ext/commands/api/cogs.html	📝 modified
ext/commands/api/context.html	📝 modified
ext/commands/api/converters.html	📝 modified
ext/commands/api/exceptions.html	📝 modified
ext/commands/api/help_commands.html	📝 modified
ext/commands/api/misc.html	📝 modified
ext/commands/api/prefix_commands.html	📝 modified