Navbar: Used new logo

[kevinrobinson]

Who is this PR for?

all users

What problem does this PR fix?

The logo on the sign in page has been updated, but the navbar when educators are signed in is still the old one.

What does this PR do?

Updates the signed in navbar to use the new logo, to match @ciscomeneses's awesome work on the sign in page in #2337.

Screenshot (if adding a client-side feature)

Checklists

Which features or pages does this PR touch?

• Core, navbar

Does this PR use tests to help verify we can deploy these changes quickly and confidently?

• Manual testing made more sense here

[kevinrobinson]

I ran into problems with the layout on IE11, so pushed a commit for that, but the signed in navbar has a similar problem, so I'll need to fix that next too.

[kevinrobinson]

Pushed another commit that fixes the layout for CSS for Internet Explorer 11. As best I understand it, the problem is that IE11 sizes SVG elements differently than Firefox, Safari and Chrome, and differently than the way it would plain HTML elements.

There's still a small alignment issue on IE11 on the sign in page that I can't figure out without breaking the other browsers, so I'm going to ship this so the new logos are out for everyone on both the sign in and signed-in pages, and then I can try to tweak the IE11 problem separately after.

[kevinrobinson]

🚢 ing this (cc @ciscomeneses)

[kevinrobinson]

This is deployed now, and looks great! 😄