Fix CI build

[piotr-roslaniec]

Type of PR:

• Other

Required reviews:

• 1

What this does:

• Installs wasm-pack from a precompiled binary
• Fixes a linting issue on Rust stable

Why it's needed:

• Some child dependencies in wasm-pack an wasm-opt get updated from time to time and that causes MSRV float
• With these changes, we should be able to avoid that in the future, and hence avoid CI breaking from time to time

[cygnusv]

Some child dependencies in wasm-pack an wasm-opt get updated from time to time and that causes MSRV float

Isn't it possible to pin all child dependencies somehow?

[piotr-roslaniec]

@cygnusv It's not a dependency of any crate, it's a utility installed on CI to compile & run WASM tests.