wasi: drop --experimental-wasm-bigint requirement

After the V8 8.5 update, the WASI APIs no longer require the
use of --experimental-wasm-bigint. This commit removes its use.

PR-URL: https://github.com/nodejs/node/pull/35415


Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Myles Borins <myles.borins@gmail.com>