Promote the NewApi check to an error again

Now that all existing cases have been baselined.

Ignore-AOSP-First: Requires a LSC that is difficult to do across branches.
Bug: 268261262
Test: m lint-check
Change-Id: I413f86ff7a1f33564465f3ba9cd52924a4242901

java/lint_test.go

@@ -91,9 +91,8 @@ 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
-		t.Error("should check NewApi warnings")
+	if !strings.Contains(*sboxProto.Commands[0].Command, "--error_check NewApi") {
+		t.Error("should check NewApi errors")
 	}
 
 	if !strings.Contains(*sboxProto.Commands[0].Command, "--error_check SomeCheck") {