fix: contribute guide link in template

[eddiezane]

Description

This PR fixes the link to the contributor guide in the PR template.

Related Issue

Fixes #

Relates to #

Type of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [x] Other (security config, docs update, etc)

Checklist before merging

• [ ] Test, docs, adr added or updated as needed
• [ ] Contributor Guide Steps followed