[HalfSheetUX] Remove explicit targetSdkVersion

Going forward targetSdkVersion would be set by build system.
It would be by default set to 10000 before SDK finalization,
and updated to the new API level after finalization.

Effectively it would mean:
1. '10000' in aosp and internal master
2. Finalized number in development branches like "33" in "tm-dev"
3. As sdk hasn't been finalised in "udc-dev", it would be "10000"
which would be automatically updated to finalized version after sdk finalization.

Removing the target sdk version declaration from the blueprint and manifest files.
More details can be found here go/mainline-modules-target-sdk-version-fix

Bug: b/242296003
Test: croot; sdks=`find ./out -name 'HalfSheetUX.apk' | grep -v .intermediates`; echo $sdks; for sdk in $sdks;do aapt2 dump badging `echo $sdk` | grep targetSdkVersion:; done
1. outputs 33 in tm-mainline-prod
2. outputs 10000 in master

Change-Id: I68120dd50c2020da7f91e29550d02b079aa61d7a
diff --git a/nearby/halfsheet/Android.bp b/nearby/halfsheet/Android.bp
index 486a3ff..c84caa6 100644
--- a/nearby/halfsheet/Android.bp
+++ b/nearby/halfsheet/Android.bp
@@ -23,7 +23,6 @@
     sdk_version: "module_current",
     // This is included in tethering apex, which uses min SDK 30
     min_sdk_version: "30",
-    target_sdk_version: "current",
     updatable: true,
     certificate: ":com.android.nearby.halfsheetcertificate",
     libs: [