refactor: fix typescript 3.7 compilation errors.

Fixes `Import declaration conflicts with local declaration` error.

Author: andrius-pra

src/components-examples/material/table/table-multiple-header-footer/table-multiple-header-footer-example.ts

@@ -1,11 +1,6 @@
 import {Component} from '@angular/core';
 import {Transaction} from '../table-footer-row/table-footer-row-example';
 
-export interface Transaction {
-  item: string;
-  cost: number;
-}
-
 /**
  * @title Table with multiple header and footer rows
  */

src/material-experimental/mdc-form-field/form-field.ts

@@ -51,9 +51,6 @@ import {MatFormFieldNotchedOutline} from './directives/notched-outline';
 import {MatPrefix} from './directives/prefix';
 import {MatSuffix} from './directives/suffix';
 
-/** Type for the available floatLabel values. */
-export type FloatLabelType = 'always' | 'auto';
-
 /** Possible appearance styles for the form field. */
 export type MatFormFieldAppearance = 'fill' | 'outline';