Bump Synapse version (0.34.1.1 -> 0.99.0rc4)

roles/matrix-synapse/defaults/main.yml

@@ -1,4 +1,4 @@
-matrix_synapse_docker_image: "matrixdotorg/synapse:v0.34.1.1-py3"
+matrix_synapse_docker_image: "matrixdotorg/synapse:v0.99.0rc4-py3"
 
 matrix_synapse_base_path: "{{ matrix_base_data_path }}/synapse"
 matrix_synapse_config_dir_path: "{{ matrix_synapse_base_path }}/config"