Fix typo in BNG lettermap

[tompeterken-os]

The tile SZ appears twice in letterMap in BNGIndexSystem.scala. One instance should read "HZ" instead. As a result, features in the HZ square are given "SZ" grid indices.

This PR makes a single update to letterMap, correcting the typo.

(Probably not spotted before now because only Fair Isle appears in the HZ square!)

Signed-off by Tom Peterken [email protected]

[milos-colic]

Hi @tompeterken-os , in order for us to proceed it is sufficient to add a comment to this PR with your sign-off (Eg. Signed-off-by: Joe Smith <[email protected]>).
We need this to make sure you are aware of the current license, and that you agree with it. :)

[codecov]

Codecov Report

Merging #433 (e69fb94) into main (19f2e9f) will increase coverage by 0.01%.
Report is 160 commits behind head on main.
The diff coverage is 97.56%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #433      +/-   ##
==========================================
+ Coverage   95.01%   95.02%   +0.01%     
==========================================
  Files         198      198              
  Lines        5658     5692      +34     
  Branches      178      175       -3     
==========================================
+ Hits         5376     5409      +33     
- Misses        282      283       +1     

Files	Coverage Δ
...bricks/labs/mosaic/core/index/BNGIndexSystem.scala	99.01% <100.00%> (ø)
...abricks/labs/mosaic/core/index/H3IndexSystem.scala	97.59% <97.50%> (-0.37%)	⬇️

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