add missing TOC entry

Author: sdgilley

articles/machine-learning/toc.yml

@@ -304,6 +304,8 @@
         - name: Compute instance
           displayName: compute target, No public IP
           href: how-to-create-manage-compute-instance.md
+        - name: Customize compute instance with a script
+          href: how-to-customize-compute-instance.md
         - name: Compute cluster
           displayName: compute target, low priority, managed identity
           href: how-to-create-attach-compute-cluster.md