Update $service_client.ts.njk

Author: sofisl

templates/esm/typescript_gapic/esm/src/$version/$service_client.ts.njk

@@ -404,7 +404,7 @@ export class {{ service.name }}Client {
         '{{ api.naming.protoPackage }}.{{ service.name }}', gapicConfig as gax.ClientConfig,
         opts.clientConfig || {}, {'x-goog-api-client': clientHeader.join(' ')}
 {%- if service.apiVersion -%}
-       , {'x-goog-api-version': {{ service.apiVersion }}}
+       , {'x-goog-api-version': '{{ service.apiVersion }}'}
 {%- endif %});
 
     // Set up a dictionary of "inner API calls"; the core implementation