tests: table-of-contents: prefer angle syntax

Let's prefer angle bracket syntax to curly syntax when invoking the
TableOfContents component in our integration tests. This will fix
deprecation warnings about using the latter, which make the test results
a bit harder to decipher.

Author: geneukum

tests/integration/components/table-of-contents-test.js

@@ -16,12 +16,12 @@ module('Integration | Component | table of contents', function (hooks) {
     this.set('classesIDs', CLASSES);
 
     await render(hbs`
-      {{
-        table-of-contents showPrivateClasses=true
-          version=emberVersion
-          classesIDs=classesIDs
-          isShowingNamespaces=true
-       }}
+      <TableOfContents
+        @showPrivateClasses={{true}}
+        @version={{this.emberVersion}}
+        @classesIDs={{this.classesIDs}}
+        @isShowingNamespaces={{true}}
+      />
     `);
 
     const contentTitle = document.querySelector(
@@ -43,12 +43,12 @@ module('Integration | Component | table of contents', function (hooks) {
     this.set('moduleIDs', MODULES);
 
     await render(hbs`
-      {{
-        table-of-contents showPrivateClasses=true
-          version=emberVersion
-          moduleIDs=moduleIDs
-          isShowingNamespaces=true
-       }}
+      <TableOfContents
+        @showPrivateClasses={{true}}
+        @version={{this.emberVersion}}
+        @moduleIDs={{this.moduleIDs}}
+        @isShowingNamespaces={{true}}
+      />
     `);
 
     const contentReference = '.toc-level-1';
@@ -73,12 +73,12 @@ module('Integration | Component | table of contents', function (hooks) {
     this.set('moduleIDs', MODULES);
 
     await render(hbs`
-      {{
-        table-of-contents showPrivateClasses=true
-          version=emberVersion
-          moduleIDs=moduleIDs
-          isShowingNamespaces=true
-       }}
+      <TableOfContents
+        @showPrivateClasses={{true}}
+        @version={{this.emberVersion}}
+        @moduleIDs={{this.moduleIDs}}
+        @isShowingNamespaces={{true}}
+      />
     `);
 
     const contentTitle = document.querySelector(
@@ -107,12 +107,12 @@ module('Integration | Component | table of contents', function (hooks) {
     this.set('moduleIDs', MODULES);
 
     await render(hbs`
-      {{
-        table-of-contents showPrivateClasses=true
-          version=emberVersion
-          moduleIDs=moduleIDs
-          isShowingNamespaces=true
-       }}
+      <TableOfContents
+        @showPrivateClasses={{true}}
+        @version={{this.emberVersion}}
+        @moduleIDs={{this.moduleIDs}}
+        @isShowingNamespaces={{true}}
+      />
     `);
 
     const titleButton = document.querySelector(