update eslint, fix eslint @typescript-eslint/no-unnecessary-type-assertion errors

[a-tarasyuk]

Based on node types stdout and columns cannot be undefined, and eslint clearly handles that case, however, Travis CI failed to run host.ts

    interface Process extends EventEmitter {
        /**
         * Can also be a tty.WriteStream, not typed due to limitation.s
         */
        stdout: WriteStream;

 columns: number;

cc @uniqueiniquity