Remove check for vscode-yaml version and `semver`

[datho7561]

semver is used to check that the version of vscode-yaml that's installed is newer than 0.0.14. That version is 6 years old, and I don't think it works properly on the latest VS Code. We should consider removing that code, then we can drop semver as a direct dependency (it will probably still be a transitive dependency though).

Originally posted by @datho7561 in #375 (comment)