Run screenshotter using Chrome 83 and Firefox 76 (#2304)

* Run screenshotter using Chrome 83 and Firefox 76

* Update screenshots

* Update NegativeSpace-chrome screenshot

The new screenshot is correct as per #1194.

* Update Units-chrome screenshot

The new screenshot is correct as per #732 and compared to Firefox.

* Update screenshots

.circleci/config.yml

@@ -4,14 +4,11 @@ executors:
   firefox:
     docker:
       - image: circleci/node:10
-      - image: selenium/standalone-firefox:2.48.2
+      - image: selenium/standalone-firefox:3.141.59-20200525
   chrome:
     docker:
       - image: circleci/node:10
-      - image: selenium/standalone-chrome:2.48.2
-        environment:
-          # workaround for https://github.com/SeleniumHQ/docker-selenium/issues/87
-          DBUS_SESSION_BUS_ADDRESS: /dev/null
+      - image: selenium/standalone-chrome:3.141.59-20200525
 
 commands:
   checkout_repo: