Fixing missing closing </li> statements in the base layout of the flaskr tutorial

[gatoniel]

I did not create an issue for this.

In my opinion, the closing tags </li> were missing in the g.user auth part of the base.html template of the flaskr tutorial. I added them in two places:

• docs/tutorial/templates.rst
• examples/tutorial/flaskr/templates/base.html

So far I have not changed the CHANGES.rst, as I think this is a minor change.

[davidism]

li does not require a closing tag. Be sure to search first before working on something like this, there are many previous closed PRs discussing it.