fix: added message in schedule bulk update

[Spandan-Mishra]

What does this PR do?

• Fixes Bulk update event types for schedule has generic success message #26333 (GitHub issue number)
• Fixes CAL-7001 (Linear issue number - should be visible at the bottom of the GitHub issue description)

Visual Demo (For contributors especially)

Image Demo (if applicable):

Before:

After:

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. If N/A, write N/A here and check the checkbox. - N/A
• I confirm automated tests are in place that prove my fix is effective or that my feature works.

How should this be tested?

1. Go to availability
2. Set any availability option as default
3. Click on update in the bulk update modal
4. See the new message showing bulk update operation as successful

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Summary by cubic

Shows a clear success toast after bulk updating selected event types to the default schedule in Availability. Replaces the generic message with a specific i18n string, addressing CAL-7001.

^{Written for commit 2e99f53. Summary will update on new commits.}

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[cubic-dev-ai]

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