fix: stabilize order of query_params (#742)

Author: busunkim96

packages/gapic-generator/gapic/templates/%namespace/%name_%version/%sub/services/%service/transports/rest.py.j2

@@ -182,9 +182,11 @@ class {{ service.name }}RestTransport({{ service.name }}Transport):
         # TODO(yon-mg): handle nested fields corerctly rather than using only top level fields
         #               not required for GCE
         query_params = {
+            {% filter sort_lines -%} 
             {%- for field in method.query_params %}
             '{{ field|camel_case }}': request.{{ field }},
             {%- endfor %}
+            {% endfilter -%} 
         }
         # TODO(yon-mg): further discussion needed whether 'python truthiness' is appropriate here
         #               discards default values