shippable.yml: Remove the Debian9-based MinGW cross-compiler tests

We're not supporting Debian 9 anymore, and we are now testing
MinGW cross-compiler builds in the gitlab-CI, too, so we do not
really need these jobs in the shippable.yml anymore.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20200921174320.46062-5-thuth@redhat.com>
Message-Id: <20200925154027.12672-13-alex.bennee@linaro.org>

.shippable.yml

@@ -7,10 +7,6 @@ env:
   matrix:
     - IMAGE=debian-amd64
       TARGET_LIST=x86_64-softmmu,x86_64-linux-user
-    - IMAGE=debian-win32-cross
-      TARGET_LIST=arm-softmmu,i386-softmmu
-    - IMAGE=debian-win64-cross
-      TARGET_LIST=aarch64-softmmu,sparc64-softmmu,x86_64-softmmu
     - IMAGE=debian-armel-cross
       TARGET_LIST=arm-softmmu,arm-linux-user,armeb-linux-user
     - IMAGE=debian-armhf-cross