chore: Remove unused work queue in Cron controller

[terrytangyuan]

Signed-off-by: terrytangyuan terrytangyuan@gmail.com

Checklist:

• My organization is added to USERS.md.

[codecov]

Codecov Report

Merging #5461 (bf4fc60) into master (3b129a8) will increase coverage by 0.16%.
The diff coverage is 32.29%.

❗ Current head bf4fc60 differs from pull request most recent head 5aa163c. Consider uploading reports for the commit 5aa163c to get more accurate results

@@            Coverage Diff             @@
##           master    #5461      +/-   ##
==========================================
+ Coverage   16.30%   16.47%   +0.16%     
==========================================
  Files         243      243              
  Lines       43675    43767      +92     
==========================================
+ Hits         7121     7209      +88     
+ Misses      35582    35575       -7     
- Partials      972      983      +11     

Impacted Files	Coverage Δ
pkg/apis/workflow/v1alpha1/generated.pb.go	0.51% <0.00%> (-0.01%)	⬇️
pkg/apis/workflow/v1alpha1/openapi_generated.go	0.00% <0.00%> (ø)
...kg/apis/workflow/v1alpha1/zz_generated.deepcopy.go	7.50% <0.00%> (+4.01%)	⬆️
workflow/cron/controller.go	0.00% <ø> (ø)
workflow/controller/operator.go	70.27% <47.36%> (-0.52%)	⬇️
pkg/apis/workflow/v1alpha1/workflow_types.go	45.52% <100.00%> (+1.98%)	⬆️
cmd/argo/commands/get.go	56.00% <0.00%> (-1.34%)	⬇️

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