Update guide rate

[wtgee]

The guide rate is used to adjust the tracking, which happens between
exposures. Typically guide rates are set at .5 * sidereal because the
correction happens during exposure so movement is minimized. Since we
are out of exposure we want the correction to happen as fast as possible.
.9 * sidereal is max.

[codecov]

Codecov Report

Merging #542 into develop will decrease coverage by 0.09%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           develop     #542     +/-   ##
==========================================
- Coverage    70.42%   70.33%   -0.1%     
==========================================
  Files           64       64             
  Lines         5484     5484             
  Branches       762      762             
==========================================
- Hits          3862     3857      -5     
- Misses        1414     1417      +3     
- Partials       208      210      +2

Impacted Files	Coverage Δ
pocs/serial_handlers/protocol_arduinosimulator.py	75.38% <0%> (-1.54%)	⬇️
pocs/observatory.py	81.59% <0%> (-0.28%)	⬇️

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