configure: remove legacy alias

Change-Id: Iabd239a311b92cb47e43666745a1e903a80aab1b
diff --git a/configure b/configure
index 0fd09e3..df467e8 100755
--- a/configure
+++ b/configure
@@ -445,7 +445,6 @@
     encode_perf_tests
     coefficient_range_checking
     lowbitdepth
-    aom_highbitdepth
     highbitdepth
     experimental
     colorspace_headers
@@ -526,9 +525,6 @@
     soft_enable convolve_round
     soft_enable aom_qm
 
-    # Backwards/jenkins compatibility with --enable-aom-highbitdepth
-    enabled aom_highbitdepth && enable_feature highbitdepth
-
     # Enable low-bitdepth pixel pipeline by default
     soft_enable lowbitdepth