C++17 is now the default.

Test: builds
Change-Id: Ibd6569c25f4ddfed3fd0cec771fba72cd5b9bd14
diff --git a/keystore-engine/Android.bp b/keystore-engine/Android.bp
index e7cd09d..60f5940 100644
--- a/keystore-engine/Android.bp
+++ b/keystore-engine/Android.bp
@@ -25,7 +25,6 @@
         "-Wall",
         "-Werror",
     ],
-    cpp_std: "c++17",
 
     shared_libs: [
         "libbinder",
@@ -58,7 +57,6 @@
         "-Werror",
         "-DBACKEND_WIFI_HIDL",
     ],
-    cpp_std: "c++17",
 
     shared_libs: [
         "android.system.wifi.keystore@1.0",