docs: update Tera links to the new URL

[dnaka91]

Description

The Tera website changed from Netlify to GitHub Pages, with the old Netlify deployment gone. Therefore, all links to Tera should point to the new URL.

Motivation and Context

How Has This Been Tested?

Clicked each link, especially the ones with anchors, and verified the anchors are still correct.

Screenshots / Logs (if applicable)

Types of Changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (no code change)
• Refactor (refactoring production code)
• Other

Checklist:

• My code follows the code style of this project.
• I have updated the documentation accordingly.
• I have formatted the code with rustfmt.
• I checked the lints with clippy.
• I have added tests to cover my changes.
• All new and existing tests passed.

[welcome]

Thanks for opening this pull request! Please check out our contributing guidelines! ⛰️

[codecov-commenter]

Codecov Report

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[orhun]

Thanks for the PR! 🐻 Can you comment on #165 about your stance on re-licensing as a future contributor?

[dnaka91]

No problem, I don't mind the re-licensing. Added my comment 🙇‍♂️

[welcome]

Congrats on merging your first pull request! ⛰️