CI: Remove build job for CONFIG_ML_PART_SPLIT

This build check was added when the tool was off by default.

Now that the tool is on by default, it is no longer required.
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 550b39b..e105588 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -231,9 +231,6 @@
         entropy-stats)
           CMAKE_FLAGS="$CMAKE_FLAGS -DCONFIG_ENTROPY_STATS=1"
           ;;
-        ml-part-split)
-          CMAKE_FLAGS="$CMAKE_FLAGS -DCONFIG_ML_PART_SPLIT=1"
-          ;;
         bawp-across-scales-fix)
           CMAKE_FLAGS="$CMAKE_FLAGS -DCONFIG_BAWP_ACROSS_SCALES_FIX=1"
           ;;
@@ -329,16 +326,6 @@
       - AOM_BUILD_CONFIG:
           - entropy-stats
 
-Build (ml-part-split):
-  extends: .build-common
-  variables:
-    # Allow build warnings.
-    EXTRA_CMAKE_FLAGS: -DENABLE_WERROR=0
-  parallel:
-    matrix:
-      - AOM_BUILD_CONFIG:
-          - ml-part-split
-
 Build (bawp-across-scales-fix):
   extends: .build-common
   parallel: