Bump babel packages to latest versions

And remove obsolete @babel packages as they are included in @babel/preset-env now: - @babel/plugin-proposal-class-properties - @babel/plugin-proposal-json-strings - @babel/plugin-proposal-private-methods - @babel/plugin-syntax-import-meta. This package was removed from the Babel configuration since we don't use it at all.

Decided to keep them as for now. Let's just update babel packages and remove obsolete istanbul packages.