fix: properly pass in ephemeral for hybrid ctx

[AstreaTSS]

Pull Request Type

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

Description

Seems like people forgot ephemeral exists for hybrid commands while testing... though it is a weird decision to use one there. Regardless, this PR fixes a bug that prevented it from working for slash command usages.

Changes

• Properly check if _slash_ctx exist when doing ephemeral checks.

Related Issues

Test Scenarios

• Make hybrid command with an ephemeral message.
• Use the slash command version.

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