Upgrade Synapse for ARM64 (v1.26.0 -> v1.28.0)

roles/matrix-synapse/defaults/main.yml

@@ -16,7 +16,7 @@ matrix_synapse_docker_image_name_prefix: "{{ 'localhost/' if matrix_synapse_cont
 # arm32 relies on self-building, so the same version can be built immediately.
 # arm64 users need to wait for a prebuilt image to become available.
 matrix_synapse_version: v1.28.0
-matrix_synapse_version_arm64: v1.26.0
+matrix_synapse_version_arm64: v1.28.0
 matrix_synapse_docker_image_tag: "{{ matrix_synapse_version if matrix_architecture in ['arm32', 'amd64'] else matrix_synapse_version_arm64 }}"
 matrix_synapse_docker_image_force_pull: "{{ matrix_synapse_docker_image.endswith(':latest') }}"