Enable tenv and testifylint rules (#32852)

Enables tenv and testifylint linters
closes: https://github.com/go-gitea/gitea/issues/32842

modules/git/grep_test.go

@@ -73,9 +73,9 @@ func TestGrepSearch(t *testing.T) {
 
 	res, err = GrepSearch(context.Background(), repo, "no-such-content", GrepOptions{})
 	assert.NoError(t, err)
-	assert.Len(t, res, 0)
+	assert.Empty(t, res)
 
 	res, err = GrepSearch(context.Background(), &Repository{Path: "no-such-git-repo"}, "no-such-content", GrepOptions{})
 	assert.Error(t, err)
-	assert.Len(t, res, 0)
+	assert.Empty(t, res)
 }