Fix small typo in partial README for UncompressedImageCore

[rvmiller89]

CompressedImageCore was duplicated in both snippets, while second snippet refers to UncompressedImageCore.

[codecov-commenter]

Codecov Report

Merging #1156 (8e9565c) into main (72ae53c) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1156   +/-   ##
=======================================
  Coverage   75.40%   75.40%           
=======================================
  Files         108      108           
  Lines        7824     7824           
=======================================
  Hits         5900     5900           
  Misses       1361     1361           
  Partials      563      563           

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[imjasonh]

Thanks!