docs: Revert removal of escape in monorepo toml example

[baluyotraf]

Description

Sorry I messed up, I forgot that you're required to escape the \ in TOML. See #1398. I should have not removed it. Though the example should still be fixed so I'm only reverting the escapes. I'm really sorry D:.

Checklist

• Add test cases to all the changes you introduce
• Run poetry all locally to ensure this change passes linter check and test
• Test the changes on the local machine manually
• Update the documentation for the changes

Expected behavior

TOML requires \ to be escaped as \\

Steps to Test This Pull Request

Additional context

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.55%. Comparing base (120d514) to head (3d0c8e0).
Report is 593 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1401      +/-   ##
==========================================
+ Coverage   97.33%   97.55%   +0.21%     
==========================================
  Files          42       57      +15     
  Lines        2104     2656     +552     
==========================================
+ Hits         2048     2591     +543     
- Misses         56       65       +9     

Flag	Coverage Δ
unittests	97.55% <ø> (+0.21%)	⬆️

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