https://blog.mozilla.org/en/firefox/better-search-suggestions/
Firefox to provide "direct results" in address bar
Where the feature is available, you can disable it by unchecking “Retrieve suggestions as you type” in the “Search” pane in Firefox settings. If this box is not yet available in your version of Firefox, you can pre-emptively disable it by setting
browser.urlbar.quicksuggest.online.enabledtofalsein about:config.