Remove OBMC from the experimental configure list

It was replaced by MOTION_VAR in commit cb60b18

Change-Id: I7ab625eef4dbae2e5585d9fa3b6873aa78b2c254
diff --git a/configure b/configure
index f7fb2ca..45bbed2 100755
--- a/configure
+++ b/configure
@@ -275,7 +275,6 @@
     ext_partition
     ext_partition_types
     ext_tile
-    obmc
     motion_var
     warped_motion
     entropy