Removing centos mirror for must-gather image

[deepakraj1997]

• centos appstream repo mirror gives 404: http://mirror.centos.org/centos-8/8/AppStream/
• http://mirror.centos.org/centos-8/8/AppStream/x86_64/
• Unable to build must-gather image locally as it fails with the 404 error.
• Was able to build successfully without the above source as it seemed to have changed.

[codecov-commenter]

Codecov Report

Merging #596 (fa57a33) into master (ce1d1fe) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #596   +/-   ##
=======================================
  Coverage   37.21%   37.21%           
=======================================
  Files          14       14           
  Lines        2937     2937           
=======================================
  Hits         1093     1093           
  Misses       1761     1761           
  Partials       83       83           

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[weshayutin]

Thanks for putting up this fix @deepakraj1997
/lgtm +1

[savitharaghunathan]

/test 4.7-operator-e2e

[openshift-ci]

@deepakraj1997: all tests passed!

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