CI: don't force testimage in fvp-base-ts

The caller should (and does) use ci/testimage.yml explicitly instead.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

ci/fvp-base-ts.yml

@@ -5,7 +5,6 @@ header:
   includes:
     - ci/fvp-base.yml
     - ci/meta-openembedded.yml
-    - ci/testimage.yml
 
 local_conf_header:
   trusted_services: |