Remove all Google Calendar references from documentation

[Copilot]

This PR removes all references to Google Calendar from the repository documentation as they are no longer relevant to the course structure.

Changes Made

The following Google Calendar references have been removed:

• README.md: Removed the Google Calendar link from the DataTalks.Club community links section
• after-sign-up.md: Removed the bullet point instructing users to subscribe to the public Google Calendar
• cohorts/2022/README.md: Removed the Google Calendar subscription link from the 2022 cohort information
• cohorts/2023/README.md: Removed the "Course Google calendar" link
• cohorts/2024/README.md: Removed the "Course Google calendar" link
• cohorts/2025/README.md: Removed the "Course Google calendar" link

All markdown formatting has been preserved, and no broken list items or formatting issues were introduced. The changes are minimal and surgical, affecting only the specific lines containing Google Calendar references.

Verification

• Confirmed no Google Calendar URLs remain in any markdown files in the repository
• All list formatting remains intact with proper structure
• No other documentation was affected by these changes

Original prompt

Remove all mentions of Google Calendar from the codebase. Specifically:

• In README.md, remove the Google Calendar link from the DataTalks.Club community section.
• In after-sign-up.md, remove references to subscribing to the public Google Calendar for course announcements.
• In cohorts/2022/README.md, remove the suggestion to subscribe to the public Google Calendar.
• In cohorts/2023/README.md, cohorts/2024/README.md, and cohorts/2025/README.md, remove the 'Course Google calendar' links from each cohort's README.

All referenced locations are confirmed by lexical search and may be incomplete, but these are the main visible places.

After removal, ensure there are no broken list items or markdown formatting issues in the affected files.

This pull request was created as a result of the following prompt from Copilot chat.

Remove all mentions of Google Calendar from the codebase. Specifically:

• In README.md, remove the Google Calendar link from the DataTalks.Club community section.
• In after-sign-up.md, remove references to subscribing to the public Google Calendar for course announcements.
• In cohorts/2022/README.md, remove the suggestion to subscribe to the public Google Calendar.
• In cohorts/2023/README.md, cohorts/2024/README.md, and cohorts/2025/README.md, remove the 'Course Google calendar' links from each cohort's README.

All referenced locations are confirmed by lexical search and may be incomplete, but these are the main visible places.

After removal, ensure there are no broken list items or markdown formatting issues in the affected files.

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