chore: Port annotations for suppressing TS 4.8 type errors. (#6075)

Googlers, see b/260116849 and cl/490119036. 

Google is internally upgrading to TS 4.8. We haven't yet upgraded so the
internal language team has asked us to annotate some code to suppress
some TS 4.8 type errors.

Author: bmd3k

tensorboard/components/tf_paginated_view/tf-category-paginated-view.ts

@@ -28,6 +28,8 @@ import {
 import {TfDomRepeat} from './tf-dom-repeat';
 
 @customElement('tf-category-paginated-view')
+// @ts-ignore(go/ts48upgrade) Fix code and remove this comment. Error:
+// TS2344: Type 'CategoryItem' does not satisfy the constraint '{}'.
 class TfCategoryPaginatedView<CategoryItem> extends TfDomRepeat<CategoryItem> {
   static readonly template = html`
     <template is="dom-if" if="[[_paneRendered]]" id="ifRendered">

tensorboard/plugins/graph/tf_graph_controls/tf-graph-controls.ts

@@ -1271,6 +1271,8 @@ class TfGraphControls extends LegacyElementMixin(
   _deviceCheckboxClicked(event: Event) {
     // Update the device map.
     const input = event.target as HTMLInputElement;
+    // @ts-ignore(go/ts48upgrade) Fix code and remove this comment. Error:
+    // TS2322: Type 'object' is not assignable to type 'DeviceForStats'.
     const devicesForStats: DeviceForStats = Object.assign(
       {},
       this.devicesForStats

tensorboard/webapp/testing/lang.ts

@@ -17,6 +17,8 @@ limitations under the License.
  * assumed not to have reference loops.
  */
 export function deepFreeze<T>(obj: T): T {
+  // @ts-ignore(go/ts48upgrade) Fix code and remove this comment. Error:
+  // TS2769: No overload matches this call.
   for (const val of Object.values(obj)) {
     if (val && typeof val === 'object') {
       deepFreeze(val);