Add Error Message for Deletion When No Args or --all Flag Specified

[danielhelfand]

Since deletion commands, with the exception of Pipeline and Task, don't require an arg anymore as part of adding --all, there should be an error message if no args are passed for deletion or the --all flag isn't used.

Currently, if a user runs something like tkn condition delete, the result would be getting a prompt like below:

Are you sure you want to delete condition  (y/n):

While this is harmless as far as deleting resources, it's not great presentation. This error message would result in the following change:

Error: must provide condition name(s) or use --all flag with delete

Submitter Checklist

• Includes tests (if functionality changed/added)
• Run the code checkers with make check
• Regenerate the manpages, docs and go formatting with make generated
• Commit messages follow commit message best practices

Release Notes

Improve deletion error message if no args or no --all flag 

[tekton-robot]

The following is the coverage report on pkg/.
Say /test pull-tekton-cli-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/helper/options/delete.go	95.5%	91.7%	-3.8

[tekton-robot]

The following is the coverage report on pkg/.
Say /test pull-tekton-cli-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/helper/options/delete.go	95.5%	95.8%	0.4

[tekton-robot]

The following is the coverage report on pkg/.
Say /test pull-tekton-cli-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/helper/options/delete.go	95.5%	95.8%	0.4

[vdemeester]

/lgtm

[tekton-robot]

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