chore(spinner): avoid deprecation warning in Safari

Fixes a deprecation warning that was being logged by the spinner on Safari.

Author: crisbeto

src/lib/progress-spinner/progress-spinner.ts

@@ -203,7 +203,7 @@ export class MatProgressSpinner extends _MatProgressSpinnerMixinBase implements
     }
 
     if (styleTag && styleTag.sheet) {
-      (styleTag.sheet as CSSStyleSheet).insertRule(this._getAnimationText());
+      (styleTag.sheet as CSSStyleSheet).insertRule(this._getAnimationText(), 0);
     }
 
     MatProgressSpinner.diameters.add(this.diameter);