Remove unused old code from gravity.sh

[rdwebdesign]

What does this PR aim to accomplish?

Remove unused/dead code from gravity.sh, forgot after a modification, 3 years ago.

Context:
The first if block inside the function was commented, making the code unconditional.
After that edition, all code after the return 0 was never executed and became useless (but we kept updating it!)

How does this PR accomplish the above?

Removing the unused code.

What documentation changes (if any) are needed to support this PR?

none

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1. I have read and understood the contributors guide, as well as this entire template. I understand which branch to base my commits and Pull Requests against.
2. I have commented my proposed changes within the code and I have tested my changes.
3. I am willing to help maintain this change if there are issues with it later.
4. It is compatible with the EUPL 1.2 license
5. I have squashed any insignificant commits. (git rebase)

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• I have read the above and my PR is ready for review. Check this box to confirm

[yubiuser]

Relevant PR: #2935

[DL6ER]

As being guilty for not removing it three years ago, I hereby approve.