Updated demos to use new Lux.PeriodicEmbedding

[nicholaskl97]

Checklist

• Appropriate tests were added
• Any code changes were done in a way that does not break public API
• All documentation related to code changes were updated
• The new code follows the
  contributor guidelines, in particular the SciML Style Guide and
  COLPRAC.
• Any new documentation only uses public API

Additional context

Instead of using WrappedFunction, there's now a Lux layer to embed $\theta$ as $(\sin \theta, \cos \theta)$, courtesy of LuxDL/Lux.jl#626.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.63%. Comparing base (96f2125) to head (1ee202f).

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #27   +/-   ##
=======================================
  Coverage   76.63%   76.63%           
=======================================
  Files          10       10           
  Lines         244      244           
=======================================
  Hits          187      187           
  Misses         57       57           

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