Remove Angular Material icon button focus

The Angular Material component library show a grey background for mat-icon-button elements. The following CSS style disables the focused background.

.mat-icon-button ::ng-deep .mat-button-focus-overlay {
    display: none;
}

From Material v15 on the HTML syntax changed:

.mat-mdc-icon-button ::ng-deep .mat-mdc-button-persistent-ripple {
    display: none;
}