chore: remove refs to deprecated io/ioutil

[testwill]

Fixes # in case of a bug fix, this should point to a bug and any other related issue(s)

Description

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review them:

• Includes unit tests
• Adds integration tests if needed.

See the contribution guide for more details.

Reviewer Notes

• The code flow looks good.
• Unit tests and or integration tests added.

Release Notes

Describe any changes here so maintainer can include it in the release notes, or delete this block.

Examples of user facing changes:
- kaniko adds a new flag `--registry-repo` to override registry

[aaron-prindle]

@testwill thanks for the PR here! We should be able to get this in if you can rebase this and fix the currently failing lint errors:
https://github.com/GoogleContainerTools/kaniko/actions/runs/6033763043/job/16402297012?pr=2716

Gofmt errors in files:
./pkg/util/transport_util.go
diff ./pkg/util/transport_util.go.orig ./pkg/util/transport_util.go
--- ./pkg/util/transport_util.go.orig
+++ ./pkg/util/transport_util.go
@@ -22,8 +22,8 @@
 	"fmt"
 	"strings"
 
-	"os"
 	"net/http"
+	"os"
 
 	"github.com/GoogleContainerTools/kaniko/pkg/config"
 	"github.com/sirupsen/logrus"
FAILED /home/runner/work/kaniko/kaniko/scripts/../hack/gofmt.sh

```pkg/util/transport_util.go:25: File is not goimports-ed (goimports)
"os"
FAILED /home/runner/work/kaniko/kaniko/scripts/../hack/linter.sh
make: *** [Makefile:67: test] Error 1

[aaron-prindle]

Created #2806 to track this refactor, closing this PR for now