Tests fail on Julia 1.10 and 1.11-rc

[davidanthoff]

I wanted to include running JuliaSyntax.jl tests into the VS Code extension release pipeline (julia-vscode/julia-vscode#3625), but it turns out that tests fail on both Julia 1.10 and 1.11-rc. And it turns out that CI here isn't run for anything newer than 1.8. I think it would generally be good if this package here ran CI on minimally all released versions regularly, plus beta or release candidates.

[LilithHafner]

CI runs on pretty much all of those (incl. 1.10 and nightly), the problem is primarily that it's failing.