Remove unused scope from Walker

The `scope` info here is entirely unused in the Glimmer codebase. It may
be used in some AST transforms, but this is fairly unlikely, since it
has only been available since Ember 3.16. Profiling template compilation
highlighted the recursive walking of the whole tree for locals in scope
during syntax parsing as a major cost in CPU usage, so the hope is that
removing this will help.

packages/@glimmer/syntax/lib/traversal/path.ts

@@ -1,11 +1,9 @@
 import * as ASTv1 from '../v1/api';
-import RootTransformScope, { TransformScope } from './scope';
 
 export default class WalkerPath<N extends ASTv1.Node> {
   node: N;
   parent: WalkerPath<ASTv1.Node> | null;
   parentKey: string | null;
-  scope: TransformScope;
 
   constructor(
     node: N,
@@ -15,20 +13,6 @@ export default class WalkerPath<N extends ASTv1.Node> {
     this.node = node;
     this.parent = parent;
     this.parentKey = parentKey;
-    this.scope = parent ? parent.scope.child(node) : new RootTransformScope(node);
-
-    // Consume in scope values
-    if (node.type === 'PathExpression') {
-      this.scope.useLocal(node);
-    }
-
-    if (node.type === 'ElementNode') {
-      this.scope.useLocal(node);
-
-      (node as ASTv1.ElementNode).children.forEach((node: ASTv1.Statement) =>
-        this.scope.useLocal(node)
-      );
-    }
   }
 
   get parentNode(): ASTv1.Node | null {