remove prescale

[baggepinnen]

The computation tested in #465 gives identical result to balance_statespace, I assume the functions are (or close to) identical.

Closes #614

[JuliaControlBot]

This is an automated message.
Plots were compared to references. 9/11 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
✔️ 0.003
✔️ 0.003
✔️ 0.0
✔️ 0.001
✔️ 0.0
✔️ 0.0
❌ 0.042
✔️ 0.006
✔️ 0.011

[codecov]

Codecov Report

Merging #620 (dff4c13) into master (35f2d67) will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #620      +/-   ##
==========================================
- Coverage   86.80%   86.77%   -0.03%     
==========================================
  Files          31       31              
  Lines        3243     3236       -7     
==========================================
- Hits         2815     2808       -7     
  Misses        428      428              

Impacted Files	Coverage Δ
src/matrix_comps.jl	92.88% <ø> (-0.20%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e4408ab...dff4c13. Read the comment docs.