rebase: bump github.com/Azure/azure-sdk-for-go/sdk/azidentity

Bumps [github.com/Azure/azure-sdk-for-go/sdk/azidentity](https://github.com/Azure/azure-sdk-for-go) from 1.5.1 to 1.6.0.
- [Release notes](https://github.com/Azure/azure-sdk-for-go/releases)
- [Changelog](https://github.com/Azure/azure-sdk-for-go/blob/main/documentation/release.md)
- [Commits](https://github.com/Azure/azure-sdk-for-go/compare/sdk/internal/v1.5.1...sdk/azcore/v1.6.0)

---
updated-dependencies:
- dependency-name: github.com/Azure/azure-sdk-for-go/sdk/azidentity
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

vendor/github.com/Azure/azure-sdk-for-go/sdk/internal/exported/exported.go

@@ -39,6 +39,11 @@ type PayloadOptions struct {
 // Subsequent reads will access the cached value.
 // Exported as runtime.Payload() WITHOUT the opts parameter.
 func Payload(resp *http.Response, opts *PayloadOptions) ([]byte, error) {
+	if resp.Body == nil {
+		// this shouldn't happen in real-world scenarios as a
+		// response with no body should set it to http.NoBody
+		return nil, nil
+	}
 	modifyBytes := func(b []byte) []byte { return b }
 	if opts != nil && opts.BytesModifier != nil {
 		modifyBytes = opts.BytesModifier