Remove deprecated GPUAdapter isFallbackAdapter (#183)

The GPUAdapterInfo isFallbackAdapter attribute has been implemented both
in [Chromium](https://issues.chromium.org/issues/409259074) and
[Firefox](https://bugzilla.mozilla.org/show_bug.cgi?id=1955057) but not
in Safari yet.

@mwyrzykowski Is that something you can address so that we can move
forward with this PR.

Author: beaufortfrancois

dist/index.d.ts

@@ -2074,13 +2074,6 @@ interface GPUAdapter {
    * </div>
    */
   readonly info: GPUAdapterInfo;
-  /**
-   * Returns the value of {@link GPUAdapter#[[adapter]]}.{@link adapter#[[fallback]]}.
-   *
-   * @deprecated Use {@link GPUAdapterInfo#isFallbackAdapter}.
-   * (Note if it's not available, it will be `undefined` which is still falsy.)
-   */
-  readonly isFallbackAdapter?: boolean;
   /**
    * Requests a device from the adapter.
    * This is a one-time action: if a device is returned successfully,
@@ -2141,10 +2134,8 @@ interface GPUAdapterInfo {
   readonly subgroupMaxSize?: number;
   /**
    * Whether the adapter is a fallback adapter.
-   *
-   * TODO: Temporarily optional until all browsers have implemented it.
    **/
-  readonly isFallbackAdapter?: boolean;
+  readonly isFallbackAdapter: boolean;
 }
 
 declare var GPUAdapterInfo: {