Fixed broken hyper links in tutorilas section

[AzamAzam]

In submitting this contribution, I agree to the current Software AG contributor agreement as referred to here:
https://github.com/quartz-scheduler/contributing/blob/main/CONTRIBUTING.md

This PR updates the hyperlinks in the tutorials section to ensure that files with the .md extension are correctly linked, resolving issues where some files were incorrectly linked with .html, leading to "Page not found" errors.

Changes

• Updated all tutorial hyperlinks from .html to .md to fix broken links.

Checklist

• tested locally
• updated the docs
• added appropriate test
• signed-off on the above mentioned SoftwareAG contributor agreement via git commit -s on my commits.
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