Check if pgcrypto already exists in anonymisation function

src/main/resources/db_scripts/create_anonymous_database.sql

@@ -1,5 +1,5 @@
 -- Note that this may require the pg_crypto extension:
-CREATE EXTENSION pgcrypto;
+CREATE EXTENSION IF NOT EXISTS pgcrypto;
 
 -- The anonymous database produced may not yet be fully anonymous due to issues with gameboards!