Make downloading and checking RTDE outputs from docs optional

[urfeex]

It's not particularly nice to require internet access to build the project every time.
Also, this reduces build requirements to run integration tests so we don't need python3 and pandas to run integration tests.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.76%. Comparing base (fbe69fc) to head (135e423).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #493      +/-   ##
==========================================
- Coverage   77.03%   76.76%   -0.28%     
==========================================
  Files         113      113              
  Lines        6045     6042       -3     
  Branches     2637     2637              
==========================================
- Hits         4657     4638      -19     
- Misses       1055     1067      +12     
- Partials      333      337       +4     

Flag	Coverage Δ
python_scripts	75.90% <ø> (ø)
start_ursim	83.08% <ø> (-2.01%)	⬇️
ur20-latest	72.34% <ø> (-0.16%)	⬇️
ur5-3.14.3	71.93% <ø> (-0.39%)	⬇️
ur5e-10.11.0	65.95% <ø> (-0.43%)	⬇️
ur5e-10.12.0	67.03% <ø> (-0.71%)	⬇️
ur5e-10.7.0	65.46% <ø> (-0.13%)	⬇️
ur5e-5.9.4	72.85% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.