build: fix demo errors

Fixes a couple of runtime errors in the MDC table and MDC form field demos.

Author: crisbeto

src/components-examples/material-experimental/mdc-table/table-expandable-rows/table-expandable-rows-example.html

@@ -5,6 +5,15 @@
     <th mat-header-cell *matHeaderCellDef> {{column}} </th>
     <td mat-cell *matCellDef="let element"> {{element[column]}} </td>
   </ng-container>
+  <ng-container matColumnDef="expand">
+    <th mat-header-cell *matHeaderCellDef aria-label="row actions">&nbsp;</th>
+    <td mat-cell *matCellDef="let element">
+      <button mat-icon-button aria-label="expand row" (click)="(expandedElement = expandedElement === element ? null : element); $event.stopPropagation()">
+        <mat-icon *ngIf="expandedElement !== element">keyboard_arrow_down</mat-icon>
+        <mat-icon *ngIf="expandedElement === element">keyboard_arrow_up</mat-icon>
+      </button>
+    </td>
+  </ng-container>
 
   <!-- Expanded Content Column - The detail row is made up of this one column that spans across all columns -->
   <ng-container matColumnDef="expandedDetail">

src/components-examples/material/table/table-expandable-rows/table-expandable-rows-example.html

@@ -7,10 +7,10 @@
   </ng-container>
   <ng-container matColumnDef="expand">
     <th mat-header-cell *matHeaderCellDef aria-label="row actions">&nbsp;</th>
-    <td mat-cell *matCellDef="let element"> 
+    <td mat-cell *matCellDef="let element">
       <button mat-icon-button aria-label="expand row" (click)="(expandedElement = expandedElement === element ? null : element); $event.stopPropagation()">
-        <mat-icon *ngIf="expandedElement !== element">keyboard_arrow_down</mat-icon> 
-        <mat-icon *ngIf="expandedElement === element">keyboard_arrow_up</mat-icon> 
+        <mat-icon *ngIf="expandedElement !== element">keyboard_arrow_down</mat-icon>
+        <mat-icon *ngIf="expandedElement === element">keyboard_arrow_up</mat-icon>
       </button>
     </td>
   </ng-container>

src/dev-app/mdc-input/mdc-input-demo.html

@@ -460,23 +460,11 @@ <h4>Textarea</h4>
 
     <p>
       Multiple hints
-      <mat-form-field appearance="fill" [color]="color" subscriptSizing="dynamic">
-        <mat-label>Fill appearance</mat-label>
-        <input matInput>
-        <mat-hint>aaa</mat-hint>
-        <mat-hint>bbb</mat-hint>
-        <mat-hint>ccc</mat-hint>
-      </mat-form-field>
-    </p>
-
-    <p>
-      Multiple hints with differing alignment
       <mat-form-field appearance="fill" [color]="color" subscriptSizing="dynamic">
         <mat-label>Fill appearance</mat-label>
         <input matInput>
         <mat-hint>aaa</mat-hint>
         <mat-hint align="end">bbb</mat-hint>
-        <mat-hint align="end">ccc</mat-hint>
       </mat-form-field>
     </p>