Remove unused imports

[srijan-paul]

Most of these imports are unnecessary, but not sure what this does:

const S = struct {
    const foo = @compileError("some message");
};

const bar = S.foo;

I've removed it for now, and the tests and the zls binary seem to work fine.

[Techatrix]

That code snippet in semantic_tokens.zig looks like something I accidentally added while testing #1764.