Require self-building of rageshake for arm64

There are no arm64 images published.. yet

group_vars/matrix_servers

@@ -2007,7 +2007,7 @@ matrix_corporal_matrix_registration_shared_secret: "{{ matrix_synapse_registrati
 # We don't enable rageshake by default.
 matrix_rageshake_enabled: false
 
-matrix_rageshake_container_image_self_build: "{{ matrix_architecture not in ['amd64', 'arm64'] }}"
+matrix_rageshake_container_image_self_build: "{{ matrix_architecture not in ['amd64'] }}"
 
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