fix: add path overlaps in manta-up svg (#10)

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## PR Checklist

- [x] Addresses an existing open issue: fixes #7 
- [x] That issue was marked as [`status: accepting
prs`](https://github.com/SquiggleTools/SquiggleConf2025/issues?q=is%3Aopen+is%3Aissue+label%3A%22status%3A+accepting+prs%22)
- [x] Steps in
[CONTRIBUTING.md](https://github.com/SquiggleTools/SquiggleConf2025/blob/main/.github/CONTRIBUTING.md)
were taken

## Overview

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-->
Fixed the manta-up svg in order to reduce the graininess issue on
rendering (in some browsers on some machines).

I wasn't able to reproduce the issue on chrome, firefox or safari on my
machine but thanks to the diligence of @teykamp he was able to
straighten things out a bit

🦦

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Co-authored-by: teykamp <thomas@eykamp.com>
Co-authored-by: Josh Goldberg <git@joshuakgoldberg.com>

Author: 3 people