Revert update to wgpu 0.20 => downgrade to wgpu 0.19.1 (#4559)

0.20 has a bunch of bugs that will be fixed by:

* gfx-rs/wgpu#5681

At Rerun, we don't want to wait for the wgpu 0.20.1 patch release before
we update egui, so we will temporarily downgrade to wgpu 0.19

After reverting I'll open a new PR that will update to 0.20 again, with
the intention of merging that once 0.20.1 is released.

.github/workflows/rust.yml

@@ -108,7 +108,7 @@ jobs:
       - name: wasm-bindgen
         uses: jetli/[email protected]
         with:
-          version: "0.2.92"
+          version: "0.2.90"
 
       - run: ./scripts/wasm_bindgen_check.sh --skip-setup