Fix typos using codespell

[ianthomas23]

Fix a number of typos by running codespell.

[codecov]

Codecov Report

Merging #1288 (371e0fa) into main (95fa9e8) will decrease coverage by 0.01%.
Report is 1 commits behind head on main.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1288      +/-   ##
==========================================
- Coverage   85.74%   85.73%   -0.01%     
==========================================
  Files          52       52              
  Lines       10870    10870              
==========================================
- Hits         9320     9319       -1     
- Misses       1550     1551       +1     

Files	Coverage Δ
datashader/colors.py	97.43% <ø> (ø)
datashader/datashape/discovery.py	94.39% <ø> (ø)
datashader/datashape/type_symbol_table.py	100.00% <ø> (ø)
datashader/datatypes.py	93.48% <ø> (-0.27%)	⬇️
datashader/reductions.py	80.62% <ø> (ø)
datashader/transfer_functions/__init__.py	87.10% <ø> (ø)

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