Add cpp20 to input vts test

We need this to take advantage of default-generated comparison
operators.

Bug: 278299254
Test: m VtsHalInputClassifierV1_0TargetTest
Change-Id: Ic03af541f2d1816efa3a1065b34b8782497db46e
diff --git a/input/classifier/1.0/vts/functional/Android.bp b/input/classifier/1.0/vts/functional/Android.bp
index 5ff1457..22346ed 100644
--- a/input/classifier/1.0/vts/functional/Android.bp
+++ b/input/classifier/1.0/vts/functional/Android.bp
@@ -25,6 +25,7 @@
 
 cc_test {
     name: "VtsHalInputClassifierV1_0TargetTest",
+    cpp_std: "c++20",
     defaults: ["VtsHalTargetTestDefaults"],
     srcs: [
         ":inputconstants_aidl",