Fix: refactored mismatching deletion resource types

[doronkg]

In cases where the resource type name mismatches in the following funcs, its deletion functionality will break:

# pkg/kor/<resource>s.go

func GetUnused<Resource>s()
    if opts.DeleteFlag {
          if diff, err = DeleteResource(diff, clientset, namespace, "<Resource>", opts.NoInteractive); err != nil {

# pkg/kor/delete.go

func DeleteResourceCmd()
        "<Resource>": func(clientset kubernetes.Interface, namespace, name string) error {

I've fixed the following mismatches in order to resolve #200:

• delete.go -> changed Roles to Role to match passed resource-type in roles.go.
• serviceaccountss.go -> changed Serviceaccount to ServiceAccount.
• statefulsets.go -> changed Statefulset to StatefulSet.

[codecov-commenter]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (47ec5b8) 44.43% compared to head (a34b248) 44.43%.

Files	Patch %	Lines
pkg/kor/delete.go	0.00%	3 Missing :warning:
pkg/kor/serviceaccounts.go	0.00%	1 Missing :warning:
pkg/kor/statefulsets.go	0.00%	1 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #201 +/- ## ======================================= Coverage 44.43% 44.43% ======================================= Files 29 29 Lines 2444 2444 ======================================= Hits 1086 1086 Misses 1205 1205 Partials 153 153 ```

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