fix rendering of some equations systems

[baggepinnen]

addresses #867

[albheim]

Haha, might have overstated the "multiple other places". Saw two and assumed there might be more... 😅

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (c7ef3b4) 92.72% compared to head (ef896d0) 92.72%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #868   +/-   ##
=======================================
  Coverage   92.72%   92.72%           
=======================================
  Files           5        5           
  Lines         330      330           
=======================================
  Hits          306      306           
  Misses         24       24           

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[JuliaControlBot]

This is an automated message.
Plots were compared to references. 11/11 images have changed, see differences below.
After pulling this PR, please update the reference images by creating a PR to ControlExamplePlots.jl here.

Difference	Reference Image	New Image
❌ 0.047
✔️ 0.011
✔️ 0.001
✔️ 0.001
✔️ 0.007
✔️ 0.003
✔️ 0.0
⚠️ 0.028
❌ 0.06
✔️ 0.0
⚠️ 0.017