Fix typos: focussed -> focused, themself -> themselves

Author: delirious-lettuce

docs/pages/upgrading.rst

@@ -19,7 +19,7 @@ in the following two places:
 - First, there was the focus which was always pointing to a
  :class:`~prompt_toolkit.buffer.Buffer` (or text input widget), but in full
  screen applications there are other widgets, like menus and buttons which
- can be focussed.
+ can be focused.
 - And secondly, it was impossible to make reusable UI components. All the key
  bindings for the entire applications were stored together in one
  ``KeyBindings`` object, and similar, all
@@ -45,7 +45,7 @@ full screen applications. These are the most important:
  Pygments tokens were not ideal for styling anything besides tokenized text.
 
  Instead we created something similar to CSS. All UI components can attach
- classnames to themself, as well as define an inline style. The final style is
+ classnames to themselves, as well as define an inline style. The final style is
  then computed by combining the inline styles, the classnames and the style
  sheet.