Properly serialize some ma1sd configuration values

We've had a report of the `connection` value getting cut off,
supposedly because it contains something that breaks off the string.

Using `|to_json` takes care of it.

roles/matrix-ma1sd/templates/ma1sd.yaml.j2

@@ -73,10 +73,10 @@ hashing:
     - none   # the same as v1 bulk lookup
     - sha256 # hash the 3PID and pepper.
   delay: 2m # how often hashes will be updated if rotation policy = per_seconds (default is 10s)
-  requests: 10 
+  requests: 10
 {% endif %}
 
 synapseSql:
-  enabled: {{ matrix_ma1sd_synapsesql_enabled }}
-  type: {{ matrix_ma1sd_synapsesql_type }}
-  connection: {{ matrix_ma1sd_synapsesql_connection }}
+  enabled: {{ matrix_ma1sd_synapsesql_enabled|to_json }}
+  type: {{ matrix_ma1sd_synapsesql_type|to_json }}
+  connection: {{ matrix_ma1sd_synapsesql_connection|to_json }}