Use 'os' instead of 'ioutil' in gazelle tests (#962)

gazelle/manifest/manifest_test.go

diff --git a/gazelle/manifest/manifest_test.go b/gazelle/manifest/manifest_test.go
index 174d999..d3873e3 100644
--- a/gazelle/manifest/manifest_test.go
+++ b/gazelle/manifest/manifest_test.go
@@ -2,7 +2,6 @@
 
 import (
 	"bytes"
-	"io/ioutil"
 	"log"
 	"os"
 	"reflect"
@@ -44,7 +43,7 @@
 			log.Println(err)
 			t.FailNow()
 		}
-		expected, err := ioutil.ReadFile("testdata/gazelle_python.yaml")
+		expected, err := os.ReadFile("testdata/gazelle_python.yaml")
 		if err != nil {
 			log.Println(err)
 			t.FailNow()

gazelle/python_test.go

diff --git a/gazelle/python_test.go b/gazelle/python_test.go
index 9965655..4fac7c0 100644
--- a/gazelle/python_test.go
+++ b/gazelle/python_test.go
@@ -24,7 +24,6 @@
 	"context"
 	"errors"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -94,9 +93,9 @@
 				continue
 			}
 
-			content, err := ioutil.ReadFile(path)
+			content, err := os.ReadFile(path)
 			if err != nil {
-				t.Errorf("ioutil.ReadFile(%q) error: %v", path, err)
+				t.Errorf("os.ReadFile(%q) error: %v", path, err)
 			}
 
 			if filepath.Base(shortPath) == "test.yaml" {