a `/` is just a `/`
a `/` is just a `/`

fixes CNVS-33496

Not sure if this was us or just the older version of MathQuill, but it
doesn't appear to be valid LaTeX to sub the string `\slash` for the `/`
character. Even MathQuill currently leaves it as is:

https://github.com/mathquill/mathquill/blob/65ce5c8f022069b54d7944c8d3d3e6c48c2365c6/src/commands/math/advancedSymbols.js#L225

It was changed ~2 years ago:

https://github.com/mathquill/mathquill/commit/72757e7ed3a50abe943cef20e5a6b69dc975b1b9

test plan:
- Navigate to a page with RCE/S.
- Open the equation editor.
- Click on the `delimeters` tab.
- Insert some content that includes the `/` character.
- Click `Switch to Advanced View`.
- Observe that the `/` is appropriately displayed.

Change-Id: I923f29db86fde37bc1a9fd9354c59525548b2921
Reviewed-on: https://gerrit.instructure.com/95926
Tested-by: Jenkins
Reviewed-by: Simon Williams <088e16a1019277b15d58faf0541e11910eb756f6@instructure.com>
QA-Review: Benjamin Christian Nelson <4a283f6b032925e40a485c88ede5597d7d65a090@instructure.com>
Product-Review: John Corrigan <3d73713d0cc718326e4fd7c06c64e067ad6e2270@instructure.com>

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