Recently Gutenberg received this commit, which made the code language selection stop showing the selected label in the toolbar. So this PR fixes it (using the same approach used for Sensei LMS plugin).
It also adds 2 small fixes:
Keys in some parts where it was missing.
Fix a style property.
Testing instructions
Create an env with WP 5.7, or with the latest Gutenberg version.
Add a SyntaxHighlighter block to a post or page.
Make sure you see and you're able to select the code language through the block toolbar.
Changes proposed in this Pull Request
Testing instructions
Screenshot / Video
https://user-images.githubusercontent.com/876340/110535739-6685e980-80ff-11eb-873a-1265099a2c3e.mov