Updating as per the virtual lab template

To make sure to follow the template of the virtual labs and to make the landing page should be the Aim page and not simulation.

Author: shraddha

experiment-descriptor.json

@@ -5,12 +5,7 @@
   "LaTeXinMD": true,
   "units": [
     {
-      "unit-type": "aim",
-      "target": "aim.html",
-      "source": "aim.md",
-      "label": "Aim",
-      "unit-type": "task",
-      "content-type": "text"
+      "unit-type": "aim"
     },
 
     {
@@ -38,7 +33,7 @@
       "content-type": "text"
     },
     {
-      "target": "index.html",
+      "target": "simulation.html",
       "source": "simulation/binary_erasure_channel.html",
       "label": "Simulation",
       "unit-type": "task",