Remove unused (?) codecov secret

[jotak]

cc @eranra @ronensc @KalmanMeth
I'm not sure who initialized the codecov action, I think Eran?
But afaik the codecov secret is only required for private repos, and moreover, I don't think it is actually set in this workflow because "GitHub’s standard pull_request workflow trigger by default prevents write permissions and secrets access to the target repository.".

[jotak]

Note than in ebpf agent repo, we don't use any codecov secret for that action: https://github.com/netobserv/netobserv-ebpf-agent/blob/main/.github/workflows/pull_request.yml#L26-L31

[codecov-commenter]

Codecov Report

Merging #400 (f903c38) into main (9740aa3) will increase coverage by 0.03%.
The diff coverage is n/a.

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@@            Coverage Diff             @@
##             main     #400      +/-   ##
==========================================
+ Coverage   61.45%   61.48%   +0.03%     
==========================================
  Files          91       91              
  Lines        6393     6393              
==========================================
+ Hits         3929     3931       +2     
+ Misses       2226     2225       -1     
+ Partials      238      237       -1     

Flag	Coverage Δ
unittests	61.48% <ø> (+0.03%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pkg/pipeline/extract/timebased/heap.go	100.00% <0.00%> (+2.17%)	⬆️

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[eranra]

@jotak, thanks. Simple is better :-)

[jotak]

/approve

[openshift-ci]

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