Migrate remaining uses of io/ioutil

See https://go.dev/doc/go1.16#ioutil

Change-Id: Ib0fa34a745f1d1515729a0eead96fe5dfcf86a21
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/77387
Auto-Submit: David Benjamin <[email protected]>
Reviewed-by: Adam Langley <[email protected]>
Commit-Queue: Adam Langley <[email protected]>
Commit-Queue: David Benjamin <[email protected]>

Author: davidben

util/fipstools/acvp/acvptool/acvp.go

@@ -29,7 +29,6 @@ import (
 	"flag"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"log"
 	"net/http"
 	neturl "net/url"
@@ -587,15 +586,15 @@ func uploadResultsDirectory(directory string, config *Config, sessionTokensCache
 
 	var results []nistUploadResult
 	// Read directory, identify, and process all files.
-	files, err := ioutil.ReadDir(directory)
+	files, err := os.ReadDir(directory)
 	if err != nil {
 		log.Fatalf("Unable to read directory: %s", err)
 	}
 
 	for _, file := range files {
 		// Add contents of the result file to results.
 		filePath := filepath.Join(directory, file.Name())
-		content, err := ioutil.ReadFile(filePath)
+		content, err := os.ReadFile(filePath)
 		if err != nil {
 			log.Fatalf("Cannot open input: %s", err)
 		}

util/fipstools/hex-search-modify.go

@@ -32,7 +32,6 @@ import (
 	"bytes"
 	"encoding/hex"
 	"fmt"
-	"io/ioutil"
 	"os"
 )
 
@@ -53,7 +52,7 @@ func main() {
 	}
 
 	// Read file contents
-	content, err := ioutil.ReadFile(filePath)
+	content, err := os.ReadFile(filePath)
 	if err != nil {
 		fmt.Fprintln(os.Stderr, "Error reading file:", err)
 		os.Exit(1)