Remove forced usage of ALPHA version of Jack

Commit 939106dc81a4f850dbf72247062ddcbd537ca413 in prebuilds/sdk
made Carnac the default Jack version.

Bug: 27376034
Change-Id: I506ae01ea7fa35fbc31f2b18cad216be1d29e77a
diff --git a/bin/vogar-android b/bin/vogar-android
index 30f0954..94e0b2c 100755
--- a/bin/vogar-android
+++ b/bin/vogar-android
@@ -13,9 +13,5 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-if [[ -z ${JACK_VERSION} ]]; then
-  export JACK_VERSION=$(basename ${ANDROID_BUILD_TOP}/prebuilts/sdk/tools/jacks/*ALPHA* | sed 's/^jack-//' | sed 's/.jar$//')
-  echo Defaulting JACK_VERSION to ${JACK_VERSION}. http://b/27376034
-fi
 vogar_jar=${OUT_DIR-${ANDROID_BUILD_TOP}/out}/host/linux-x86/framework/vogar.jar
 exec java -classpath ${vogar_jar} vogar.Vogar "$@"