tasks: Install full chromium

The headless version has several bugs, at least [1] and [2]. Also,
headless and full Chromium render texts slightly differently, so we
can't debug/fix pixel tests with `TEST_SHOW_BROWSER=pixels`.

This is a net 100 MB size increase of the tasks container, and will
break all pixel tests once, but long-term it is a better browser.

[1] https://issues.redhat.com/browse/COCKPIT-1159
[2] cockpit-project/cockpit-files#911 (comment)

tasks/container/Containerfile

@@ -7,7 +7,7 @@ RUN dnf -y update && \
         adobe-source-code-pro-fonts \
         byobu \
         chromedriver \
-        chromium-headless \
+        chromium \
         curl \
         dbus-daemon \
         dbus-glib \