fix(helm): explicitly specify curl in probeWebhook

[stek29]

What this PR does / why we need it:
Add curl as first argument of probeWebhook container, so it's possible to use different images which do have curl but don't have curl set as an entrypoint.

this is exactly what entrypoint of curlimages/curl does: it adds curl if first argument is not a valid command:
https://github.com/curl/curl-docker/blob/28034fa450ec24aa79cb17fe65b00eda85ae3e2c/alpine/latest/entrypoint.sh#L10-L12

[codecov-commenter]

Codecov Report

Merging #2207 (6a440b4) into master (46547db) will increase coverage by 0.08%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2207      +/-   ##
==========================================
+ Coverage   54.33%   54.42%   +0.08%     
==========================================
  Files         111      111              
  Lines        9529     9529              
==========================================
+ Hits         5178     5186       +8     
+ Misses       3952     3946       -6     
+ Partials      399      397       -2     

Flag	Coverage Δ
unittests	54.42% <ø> (+0.08%)	⬆️

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

Impacted Files	Coverage Δ
pkg/readiness/object_tracker.go	82.91% <0.00%> (-1.07%)	⬇️
...onstrainttemplate/constrainttemplate_controller.go	56.59% <0.00%> (+1.67%)	⬆️
pkg/watch/replay.go	81.25% <0.00%> (+2.27%)	⬆️

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[maxsmythe]

LGTM