chore: Add missing slash

Author: lqiu96

gax-java/gax-grpc/src/main/resources/META-INF/native-image/com.google.api/gax-grpc/native-image.properties

@@ -14,5 +14,5 @@ Args=--add-opens=java.base/java.time=ALL-UNNAMED \
     io.grpc.netty.shaded.io.netty.util.internal.PlatformDependent,\
     io.grpc.netty.shaded.io.netty.util.internal.shaded.org.jctools.queues.unpadded.MpscUnpaddedArrayQueue,\
     io.grpc.netty.shaded.io.netty.buffer.PoolThreadCache,\
-    io.grpc.netty.shaded.io.netty
+    io.grpc.netty.shaded.io.netty \
   --features=com.google.api.gax.grpc.nativeimage.GrpcNettyFeature