Links to Markown Cheatsheet outdated

[menschenkind]

Description

The Markdown cheatsheet PDF link in issue templates 1, 3, and 4 is outdated and should be updated to the correct version.

Steps to reproduce

1. Open issue template 1, 3, or 4.
2. Scroll to the section with the Markdown cheatsheet link.
3. Click the link → it points to an outdated PDF.

Expected behavior

The link should point to the current Markdown cheatsheet PDF.

Links to the affected lines

• issue1.md#L15
• issue3.md#L15
• issue4.md#L14