feat: add fail_if_not_exists for PrefixedContext.reply

[AstreaTSS]

Pull Request Type

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

Description

This is a simple PR to add fail_if_not_exists to PrefixedContext.reply. Really, I have to question why fail_if_not_exists doesn't default to False - regardless, people at least have the option now.

Changes

• Add fail_if_not_exists to PrefixedContext.reply.

Related Issues

Test Scenarios

@prefixed_command()
async def some_cmd(ctx: PrefixedContext):
    await ctx.message.delete()
    await ctx.reply("Hello!")  # will fail
    # meanwhile, await ctx.reply("Hello!", fail_if_not_exists=False) will work with this PR

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

[FayeDel]

Can't currently test, but looks good to me 👍🏻