Update old field classification naming

[jatkinson1000]

To be consistent with old indoor classification naming.

[TomHall2020]

Yup, I definitely would have wanted to make that rename as part of the structure of #103 but good to have it locked in place already and I wouldn't have caught renaming the test functions and extra bits of documentation.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.81%. Comparing base (e0d8d00) to head (70cd955).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #107   +/-   ##
=======================================
  Coverage   97.81%   97.81%           
=======================================
  Files          30       30           
  Lines        1742     1742           
=======================================
  Hits         1704     1704           
  Misses         38       38           

Files with missing lines	Coverage Δ
archeryutils/classifications/__init__.py	100.00% <ø> (ø)
...s/classifications/agb_old_field_classifications.py	100.00% <100.00%> (ø)
...cheryutils/classifications/tests/test_agb_field.py	100.00% <ø> (ø)
...yutils/classifications/tests/test_agb_old_field.py	100.00% <100.00%> (ø)