perf(material/button): Remove unused inject.

Author: kseamon

src/material/button/button-base.ts

@@ -91,7 +91,6 @@ const HOST_SELECTOR_MDC_CLASS_PAIR: {attribute: string; mdcClasses: string[]}[]
 @Directive()
 export class MatButtonBase implements AfterViewInit, OnDestroy {
   _elementRef = inject(ElementRef);
-  _platform = inject(Platform);
   _ngZone = inject(NgZone);
   _animationMode = inject(ANIMATION_MODULE_TYPE, {optional: true});