test: Use testing.T.Cleanup to remove tempdirs

internal/cache/testing.go

@@ -9,12 +9,12 @@ import (
 
 // TestNewCache returns a cache in a temporary directory which is removed when
 // cleanup is called.
-func TestNewCache(t testing.TB) (*Cache, func()) {
-	dir, cleanup := test.TempDir(t)
+func TestNewCache(t testing.TB) *Cache {
+	dir := test.TempDir(t)
 	t.Logf("created new cache at %v", dir)
 	cache, err := New(restic.NewRandomID().String(), dir)
 	if err != nil {
 		t.Fatal(err)
 	}
-	return cache, cleanup
+	return cache
 }