Update wording in LDA docs

[ericstj]

Update the wording mentioning countries. This is actually a quote, but it need not mention countries - the actual source of this quote has since been updated.
https://en.wikipedia.org/w/index.php?title=Earth_Day&oldid=824511329 (which was pulled from an old version of earthday.org).

I didn't bother updating the values in the comment - I'm not sure if they need to be accurate to get the point across. @michaelgsharp if you think they should be updated please let me know and help me recompute them.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.78%. Comparing base (be1e428) to head (532de28).
Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7253      +/-   ##
==========================================
+ Coverage   68.77%   68.78%   +0.01%     
==========================================
  Files        1462     1463       +1     
  Lines      272261   272288      +27     
  Branches    28176    28177       +1     
==========================================
+ Hits       187254   187304      +50     
+ Misses      77764    77741      -23     
  Partials     7243     7243              

Flag	Coverage Δ
Debug	68.78% <ø> (+0.01%)	⬆️
production	63.29% <ø> (+0.01%)	⬆️
test	89.04% <ø> (+<0.01%)	⬆️

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Files with missing lines	Coverage Δ
src/Microsoft.ML.Transforms/Text/LdaTransform.cs	88.44% <ø> (ø)

... and 10 files with indirect coverage changes

[ericstj]

Failure downloading tokenizer vocab file