[chore] - ioutil.ReadFile is deprecated (#753)

* Use os.ReadFile.

* Update imports.

* remove unused import.

hack/generate/generate.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"fmt"
-	"io/ioutil"
 	"log"
 	"os"
 	"path/filepath"
@@ -77,7 +76,7 @@ func mustWriteTemplates(jobs []templateJob) {
 
 	// Write the files from templates.
 	for _, job := range jobs {
-		tmplBytes, err := ioutil.ReadFile(job.TemplatePath)
+		tmplBytes, err := os.ReadFile(job.TemplatePath)
 		if err != nil {
 			log.Fatal(err)
 		}