build(deps): bump wasm-bindgen-futures from 0.4.20 to 0.4.21

Bumps [wasm-bindgen-futures](https://github.com/rustwasm/wasm-bindgen) from 0.4.20 to 0.4.21.
- [Release notes](https://github.com/rustwasm/wasm-bindgen/releases)
- [Changelog](https://github.com/rustwasm/wasm-bindgen/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rustwasm/wasm-bindgen/commits)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Cargo.lock

@@ -2138,9 +2138,9 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen-futures"
-version = "0.4.20"
+version = "0.4.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3de431a2910c86679c34283a33f66f4e4abd7e0aec27b6669060148872aadf94"
+checksum = "8e67a5806118af01f0d9045915676b22aaebecf4178ae7021bc171dab0b897ab"
 dependencies = [
  "cfg-if 1.0.0",
  "js-sys",