fix: updatre prom client due to breaking change

[dalehille]

209175e
https://github.com/siimon/prom-client/releases

If your metrics server has a line like res.send(register.metrics()), you
should change it to res.send(await register.metrics()).

The error message was:

The first argument must be of type string or an instance of Buffer, ArrayBuffer, or Array or an Array-like Object. Received an instance of PromisenameTypeErrorstackTypeError [ERR_INVALID_ARG_TYPE]: The first argument must be of type string or an instance of Buffer, ArrayBuffer, or Array or an Array-like Object. Received an instance of Promise
    at Function.from (buffer.js:330:9)
    at toBuffer (/home/node/node_modules/compression/index.js:286:14)
    at ServerResponse.end (/home/node/node_modules/compression/index.js:115:22)
    at /home/node/app/index.js:80:12
    at Layer.handle [as handle_request] (/home/node/node_modules/express/lib/router/layer.js:95:5)
    at next (/home/node/node_modules/express/lib/router/route.js:137:13)
    at Route.dispatch (/home/node/node_modules/express/lib/router/route.js:112:3)
    at Layer.handle [as handle_request] (/home/node/node_modules/express/lib/router/layer.js:95:5)
    at /home/node/node_modules/express/lib/router/index.js:281:22
    at Function.process_params (/home/node/node_modules/express/lib/router/index.js:335:12)
    at next (/home/node/node_modules/express/lib/router/index.js:275:10)
    at /home/node/node_modules/i18next-http-middleware/cjs/index.js:123:14
    at I18n.loadLanguages (/home/node/node_modules/i18next/dist/cjs/i18next.js:2247:23)
    at i18nextMiddleware (/home/node/node_modules/i18next-http-middleware/cjs/index.js:122:13)
    at Layer.handle [as handle_request] (/home/node/node_modules/express/lib/router/layer.js:95:5)
    at trim_prefix (/home/node/node_modules/express/lib/router/index.js:317:13)
    at /home/node/node_modules/express/lib/router/index.js:284:7
    at Function.process_params (/home/node/node_modules/express/lib/router/index.js:335:12)
    at next (/home/node/node_modules/express/lib/router/index.js:275:10)
    at Layer.handle [as handle_request] (/home/node/node_modules/express/lib/router/layer.js:91:12)
    at trim_prefix (/home/node/node_modules/express/lib/router/index.js:317:13)
    at /home/node/node_modules/express/lib/router/index.js:284:7