Allow lsp UI doc hide from focused frame

[Lenbok]

Previously, calling lsp-ui-doc-hide-frame would not hide the frame when the user focus was inside the frame.

Now in your use-package you can have something like:

  :bind (:map lsp-ui-doc-frame-mode-map
              ("q" . 'lsp-ui-doc-hide)
              ("u" . 'lsp-ui-doc-unfocus-frame))

This is regardless of whether the doc frame was instigated by lsp-ui-doc-show, lsp-ui-doc-glance, or cursor/mouse hover.

Fixes #726

@kiennq