Promote NewApi to an error again

Now that issues have been baselined.

Bug: 268261262
Test: Presubmits
Change-Id: I3a1591d650fc46f67426d0f64162d261a24aa6eb

java/lint_test.go

@@ -113,8 +113,7 @@ func TestJavaLintUsesCorrectBpConfig(t *testing.T) {
 		t.Error("did not use the correct file for baseline")
 	}
 
-	if !strings.Contains(*sboxProto.Commands[0].Command, "--warning_check NewApi") {
-		// TODO(b/268261262): Change this to check for --error_check
+	if !strings.Contains(*sboxProto.Commands[0].Command, "--error_check NewApi") {
 		t.Error("should check NewApi warnings")
 	}