tests fixed

Author: kseamon

src/material-experimental/mdc-table/table.scss

@@ -1,4 +1,9 @@
+@use '../../material/core/style/vendor-prefixes';
 @import '@material/data-table/mixins.import';
 @import '../mdc-helpers/mdc-helpers';
 
 @include mdc-data-table-core-styles($query: $mat-base-styles-without-animation-query);
+
+.mat-table-sticky {
+  @include vendor-prefixes.position-sticky;
+}

src/material-experimental/mdc-table/table.ts

@@ -27,6 +27,9 @@ export class MatTable<T> extends CdkTable<T> implements OnInit {
   /** Overrides the sticky CSS class set by the `CdkTable`. */
   protected stickyCssClass = 'mat-mdc-table-sticky';
 
+  /** Overrides the need to add position: sticky on every sticky cell element in `CdkTable`. */
+  protected needsPositionStickyOnElement = false;
+
   // After ngOnInit, the `CdkTable` has created and inserted the table sections (thead, tbody,
   // tfoot). MDC requires the `mdc-data-table__content` class to be added to the body.
   ngOnInit() {