Remove dot from gstreamer test definition name

This is in order to keep consistency between the test definition name
and the file name, at the same time of following the same standard for
the rest of the test cases.

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

test-cases/apparmor-gstreamer1-0.yaml

 metadata:
-  name: apparmor-gstreamer1.0
+  name: apparmor-gstreamer1-0
   format: "Apertis Test Definition 1.0"
   image-types:
     target:  [ armhf-internal, amd64 ]

test-cases/gstreamer1-0-decode.yaml

 metadata:
-  name: gstreamer1.0-decode
+  name: gstreamer1-0-decode
   format: "Apertis Test Definition 1.0"
   image-types:
     minimal: [ armhf-internal, armhf, arm64, amd64 ]