fix(form-field): add missing material common module

We seem to miss the `MatCommonModule` in the form-field. This came up
when doing size comparison between the MDC-based form-field.

Author: devversion

src/material/form-field/form-field-module.ts

@@ -6,9 +6,10 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import {ObserversModule} from '@angular/cdk/observers';
 import {CommonModule} from '@angular/common';
 import {NgModule} from '@angular/core';
-import {ObserversModule} from '@angular/cdk/observers';
+import {MatCommonModule} from '@angular/material/core';
 import {MatError} from './error';
 import {MatFormField} from './form-field';
 import {MatHint} from './hint';
@@ -29,9 +30,11 @@ import {MatSuffix} from './suffix';
   ],
   imports: [
     CommonModule,
+    MatCommonModule,
     ObserversModule,
   ],
   exports: [
+    MatCommonModule,
     MatError,
     MatFormField,
     MatHint,