Remove redundant IsExternalInit package

[atifaziz]

This PR removes the IsExternalInit package reference from the test project that's redundant with PolySharp.

[codecov]

Codecov Report

Merging #1022 (f4dd231) into master (66f7cab) will not change coverage.
The diff coverage is n/a.

❗ Current head f4dd231 differs from pull request most recent head 17c6201. Consider uploading reports for the commit 17c6201 to get more accurate results

@@           Coverage Diff           @@
##           master    #1022   +/-   ##
=======================================
  Coverage   92.63%   92.63%           
=======================================
  Files         113      113           
  Lines        3421     3421           
  Branches     1056     1056           
=======================================
  Hits         3169     3169           
  Misses        189      189           
  Partials       63       63           

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more