Remove the explict package dependency on mktemp

Remove this package dependency from the dbus-installed-tests test case
since this package is already installed by coreutils.

Signed-off-by: Luis Araujo <luis.araujo@collabora.co.uk>

test-cases/dbus-installed-tests.yaml

@@ -23,7 +23,6 @@ install:
     - libdbus-1-3-dbgsym
     - dbus-tests-dbgsym
     - dbus-dbgsym
-    - mktemp
   git-repos:
     - url: https://gitlab.apertis.org/infrastructure/apertis-tests.git
       branch: 'apertis/v2019pre'