Remove bedrock-hello-world repo ref.

[BigBlueHat]

We've archived bedrock-hello-world in favor of bedrock-examples.

[codecov]

Codecov Report

Merging #122 (017dc5f) into main (7075f27) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #122   +/-   ##
=======================================
  Coverage   81.45%   81.45%           
=======================================
  Files          10       10           
  Lines        1941     1941           
=======================================
  Hits         1581     1581           
  Misses        360      360           

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