docs(cli): fix cron delete flag description

[tczhao]

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[codecov]

Codecov Report

Merging #7058 (a1222c2) into master (4734cbc) will decrease coverage by 0.00%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #7058      +/-   ##
==========================================
- Coverage   48.54%   48.53%   -0.01%     
==========================================
  Files         265      265              
  Lines       19307    19307              
==========================================
- Hits         9372     9371       -1     
  Misses       8880     8880              
- Partials     1055     1056       +1     

Impacted Files	Coverage Δ
cmd/argo/commands/cron/delete.go	0.00% <0.00%> (ø)
cmd/argoexec/commands/emissary.go	50.35% <0.00%> (-1.44%)	⬇️
cmd/argo/commands/get.go	59.18% <0.00%> (-0.59%)	⬇️
workflow/controller/operator.go	71.29% <0.00%> (+0.14%)	⬆️

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