DANDI & BICAN: Default interface to lab

Earlier was just defaulting the first profile item to lab.
I'll add this to the spec on the image.

Ref 2i2c-org#3827
Ref 2i2c-org#3824

Author: yuvipanda

config/clusters/bican/common.values.yaml

@@ -48,14 +48,14 @@ jupyterhub:
           - satra
           - djarecka
   singleuser:
+    defaultUrl: /lab
     profileList:
       - display_name: "DANDI (CPU)"
         description: "Default DANDI image with JupyterLab"
         default: true
         kubespawner_override:
           image: dandiarchive/dandihub:latest
           image_pull_policy: Always
-          default_url: /lab
         profile_options: &profile_options_cpu
           requests:
             display_name: Resource Allocation

config/clusters/dandi/common.values.yaml

@@ -50,14 +50,14 @@ jupyterhub:
     userScheduler:
       enabled: true
   singleuser:
+    defaultUrl: /lab
     profileList:
       - display_name: "DANDI (CPU)"
         description: "Default DANDI image with JupyterLab"
         default: true
         kubespawner_override:
           image: dandiarchive/dandihub:latest
           image_pull_policy: Always
-          default_url: /lab
         profile_options: &profile_options_cpu
           requests:
             display_name: Resource Allocation