fix helm copy typo in Dockerfile.prow

[xiangjingli]

• I have taken backward compatibility into consideration.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (85bd342) 55.19% compared to head (b34f1c1) 55.63%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #390      +/-   ##
==========================================
+ Coverage   55.19%   55.63%   +0.43%     
==========================================
  Files          71       71              
  Lines       15315    15315              
==========================================
+ Hits         8453     8520      +67     
+ Misses       6017     5940      -77     
- Partials      845      855      +10     

Flag	Coverage Δ
unit	55.63% <ø> (+0.43%)	⬆️

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[mikeshng]

/lgtm

/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mikeshng, xiangjingli

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