Updated Djblets' ListItemView to use the correct CSS class. More 

specifically ListItemView was using djblets-c-config-forms-list-item 

instead of djblets-c-config-forms-list__item.

I did not run any automated tests, instead I verified that the

change was successful by accessing fields where ListItemView was 

being used. I manually verified that the correct CSS class was 

being used with Google Chrome Developer Tools. Examples of 

this were in Review Board's user preferences page, in sections 

such as "Groups" or "Authentication > API Tokens".