Revert "ci: Freeze rustc for nightly web builds to 1.81.0"

[torokati44]

Reverts #18397.

To be merged once wasm-bindgen/wasm-bindgen#4213 is merged and released, so wasm-bindgen/wasm-bindgen#4227 can be fixed properly.

Also referencing wasm-bindgen/wasm-bindgen#4211.

[danielhjacobs]

Referencing #18528

[danielhjacobs]

Two options for merging this PR:

1. Merge web: Make npm run build:dual-wasm create an MVP vanilla WASM module and make the default WASM module be with extensions #18528, integrate it into CI with these commands: web: Make npm run build:dual-wasm create an MVP vanilla WASM module and make the default WASM module be with extensions #18528 (comment), and then merge this, therefore supporting all the browsers we currently support.
2. Accept the loss of Pale Moon support, Basilisk support, and Safari 14.1 as acceptable, announce it, note it on https://github.com/ruffle-rs/ruffle/wiki#web, merge web: Improve error when WASM extensions are unsupported but only the module which uses them is available #18838, and then merge this, therefore adding a message that browsers without reference-types are unsupported.