CI: Disable native Windows builds for now

These are extremely slow (the image build is currently at 36 minutes
and still running) which is standing in the way of us having functional
CI at all. They can be re-enabled if someone will maintain them.

Signed-off-by: Simon McVittie <smcv@collabora.com>

.gitlab-ci.yml

@@ -130,6 +130,8 @@ windows amd64 image:
         echo "Failed to build the image"
         Exit 1
       }
+  # This is extremely slow, and is getting in the way of having CI at all
+  when: manual
 
 .unix-host-build:
   stage: build
@@ -351,6 +353,8 @@ ubuntu jammy autotools:
     - $WarningPreference = "Stop"
     - $env:DBUS_TEST_MALLOC_FAILURES = 0
     - $env:PATH += ";C:\bin"
+  # These are extremely slow, and are getting in the way of having CI at all
+  when: manual
 
 windows msys64 ucrt64 cmake:
   extends: .win-build