Remove deprecated/unused fastScrollModifier

typings/xterm.d.ts

@@ -107,13 +107,6 @@ declare module '@xterm/xterm' {
      */
     drawBoldTextInBrightColors?: boolean;
 
-    /**
-     * The modifier key hold to multiply scroll speed.
-     * @deprecated This option is no longer available and will always use alt.
-     * Setting this will be ignored.
-     */
-    fastScrollModifier?: 'none' | 'alt' | 'ctrl' | 'shift';
-
     /**
      * The scroll speed multiplier used for fast scrolling when `Alt` is held.
      */