Fix defn and test of test_sphlat().

[fyellin]

Fix Issue #471 Fix definition of sphlat(). Create new test.

Note. Calculation performed by this function is just (r, phi, theta) -> (r, theta, π/2 - phi)

[codecov[bot]]

Codecov Report

Merging #472 (c33f18f) into main (c01d8ce) will not change coverage. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #472   +/-   ##
=======================================
  Coverage   99.86%   99.86%           
=======================================
  Files          13       13           
  Lines       15635    15635           
=======================================
  Hits        15614    15614           
  Misses         21       21           

Files Changed	Coverage Δ
src/spiceypy/spiceypy.py	99.68% <100.00%> (ø)
src/spiceypy/tests/test_wrapper.py	100.00% <100.00%> (ø)