Prune outdated docs info from manifest schema. (#762)

src/rustdoc_schema.graphql

@@ -35,11 +35,7 @@ type Crate {
   item: [Item!]
 
   """
-  User-facing features that are present in the crate.
-
-  We heuristically disregard features prefixed with `_`, and features introduced by
-  optional dependencies that are never referenced by any other feature.
-  We deem those features to be non-user-facing, and do not show them here.
+  Features that are present in the crate.
 
   If feature data is not loaded into the adapter, this edge will not have any instances.
   """
@@ -49,11 +45,8 @@ type Crate {
   User-facing features that are enabled by default, either directly or transitively.
 
   Directly enabled features are explicitly enabled by the `default` feature. Such features
-  may in turn enable other features, and so on — those are transitively enabled default features.
-
-  We heuristically disregard features prefixed with `_`, and features introduced by
-  optional dependencies that are never referenced by any other feature.
-  We deem those features to be non-user-facing, and do not show them here.
+  may in turn enable other features, and so on — those are *transitively* enabled default features,
+  which are not included here.
 
   If feature data is not loaded into the adapter, this edge will not have any instances.
   """