Noslip arachne.yml (#1739)

<!--
This is a semi-strict format, you can add/remove sections as needed but
the order/format should be kept the same
Remove these comments before submitting
-->

# Description

<!--
Explain this PR in as much detail as applicable

Some example prompts to consider:
How might this affect the game? The codebase?
What might be some alternatives to this?
How/Who does this benefit/hurt [the game/codebase]?
-->

Literally one line changed, makes arachne incapable of slipping. They
have 8 legs, and realistically losing footing with one of them wouldn't
cause them to tumble over. I feel like this just makes sense, and it
would be a nice QoL change for Arachne' who definitely need it.





---

<!--
This is default collapsed, readers click to expand it and see all your
media
The PR media section can get very large at times, so this is a good way
to keep it clean
The title is written using HTML tags
The title must be within the <summary> tags or you won't see it
-->

<details><summary><h1>Media</h1></summary>
<p>

![Example Media Embed](https://example.com/thisimageisntreal.png)

</p>
</details>

---

# Changelog

<!--
You can add an author after the `:cl:` to change the name that appears
in the changelog (ex: `:cl: Death`)
Leaving it blank will default to your GitHub display name
This includes all available types for the changelog
-->

:cl:
-add: Arachne are immune to slipping

---------

Signed-off-by: EctoplasmIsGood <109397347+EctoplasmIsGood@users.noreply.github.com>
Signed-off-by: sleepyyapril <123355664+sleepyyapril@users.noreply.github.com>
Co-authored-by: sleepyyapril <123355664+sleepyyapril@users.noreply.github.com>

Resources/Prototypes/Entities/Mobs/Species/arachne.yml

@@ -234,3 +234,4 @@
     templateId: anytaur
   - type: HumanoidAppearance
     species: Arachne
+  - type: NoSlip