Simplify tutorial script for computing the radiation pattern of an antenna above a ground plane in 1D

[oskooi]

This PR simplifies the example script for Tutorial/Antenna above a Perfect Electric Conductor Ground Plane. Previously, this script involved a calculation of the radiation pattern in free space which has been removed as it is not necessary.

These changes are in preparation for a unit test for boundary conditions in 1D that will be added shortly which will be based on this calculation.

[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.84%. Comparing base (f29a8c7) to head (edca75c).
⚠️ Report is 92 commits behind head on master.
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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3119      +/-   ##
==========================================
+ Coverage   73.81%   73.84%   +0.02%     
==========================================
  Files          18       18              
  Lines        5423     5452      +29     
==========================================
+ Hits         4003     4026      +23     
- Misses       1420     1426       +6     

see 1 file with indirect coverage changes

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