fix(ci) kumactl test output matching

[jpeach]

Summary

This test failure is a result of the combination of #2419 and #2438.

The fix is to test for error output using a substring match, which was
already done in most places in #2438, but this instance was overlooked.

Full changelog

N/A

Issues resolved

N/A

Documentation

NA

Testing

• Unit tests
• E2E tests
• Manual testing on Universal
• Manual testing on Kubernetes

Backwards compatibility

• Add backport-to-stable label if the code is backwards compatible. Otherwise, list breaking changes.

[codecov-commenter]

Codecov Report

Merging #2446 (bb90794) into master (2bc0a3f) will increase coverage by 0.00%.
The diff coverage is 85.71%.

@@           Coverage Diff           @@
##           master    #2446   +/-   ##
=======================================
  Coverage   52.55%   52.55%           
=======================================
  Files         878      879    +1     
  Lines       47904    47923   +19     
=======================================
+ Hits        25177    25188   +11     
- Misses      20680    20684    +4     
- Partials     2047     2051    +4     

Impacted Files	Coverage Δ
app/kumactl/cmd/root.go	73.68% <50.00%> (-5.57%)	⬇️
pkg/util/test/mock_api_client.go	100.00% <100.00%> (ø)
app/kumactl/pkg/resources/apiserver_client.go	35.00% <0.00%> (-45.00%)	⬇️
pkg/insights/components.go	70.00% <0.00%> (-30.00%)	⬇️
app/kumactl/pkg/client/api_server_client.go	66.66% <0.00%> (-16.67%)	⬇️
app/kumactl/pkg/resources/request.go	50.00% <0.00%> (-14.29%)	⬇️
pkg/util/http/tls.go	70.00% <0.00%> (-10.00%)	⬇️
pkg/insights/resyncer.go	64.70% <0.00%> (-0.85%)	⬇️
... and 4 more

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[bartsmykla]

lgtm