setup: Rename postgresql-init-db to create-database.

The old name was confusingly similar to initialize-database.

scripts/lib/install

@@ -500,7 +500,7 @@ EOF
 fi
 
 if has_class "zulip::postgresql_common" && [ -z "$NO_INIT_DB" ]; then
-    "$ZULIP_PATH"/scripts/setup/postgresql-init-db
+    "$ZULIP_PATH"/scripts/setup/create-database
 fi
 
 if has_class "zulip::app_frontend_base"; then