Remove release debug combo

.travis.yml

@@ -168,7 +168,7 @@ script:
     - if [[ "$ASAN" == "on" ]]; then export ASANVARIANT="${ASANVARIANT} on"; fi
 
     - |
-      for build_type in debug minsizerel relwithdebinfo release; do
+      for build_type in debug minsizerel release; do
         for asan_type in ASANVARIANT; do
           build_dir="build-$build_type-asan-$asan_type"
           mkdir $build_dir