Set min_sdk_version to 31 for CtsHostsideNetworkTestsAidl.

This allows CtsHostideNetworkTests to run on S. Setting minsdk
to S is required because if the minsdk is T or above, the AIDL
compiler will generate code that contains Parcel#obtain(IBinder),
which only exists on T+.

Fix: 365129333
Test: atest CtsHostsideNetworkTests passes on redfin running S
Change-Id: Icac58bcc27194129014a0d615b5ca43b8f352ebd
diff --git a/tests/cts/hostside/aidl/Android.bp b/tests/cts/hostside/aidl/Android.bp
index 33761dc..8ec9284 100644
--- a/tests/cts/hostside/aidl/Android.bp
+++ b/tests/cts/hostside/aidl/Android.bp
@@ -20,6 +20,7 @@
 java_test_helper_library {
     name: "CtsHostsideNetworkTestsAidl",
     sdk_version: "current",
+    min_sdk_version: "31",
     srcs: [
         "com/android/cts/net/hostside/*.aidl",
         "com/android/cts/net/hostside/*.java",