docs: Remove the manually-generated env var reference page and its links

Maybe configuration.mdx could be rewritten for better clarity on
converting between config param <-> env var

docs/reference/_meta.json

@@ -4,11 +4,6 @@
         "name": "config",
         "label": "Configuration"
     },
-    {
-        "type": "file",
-        "name": "environment-variables",
-        "label": "Environment Variables"
-    },
     {
         "type": "file",
         "name": "admin",