fix: await promise when setting user agent (#1113)

Some of my devices were bugging out because the setUserAgent didn't had an await, after this everything was working fine (try loading the wwebjs in a broken microSd ahhaha).

We need some testing but on my limited testing everything is working

Co-authored-by: Rajeh Taher <rajeh@reforward.dev>

src/Client.js

@@ -76,7 +76,7 @@ class Client extends EventEmitter {
             page = (await browser.pages())[0];
         }        
         
-        page.setUserAgent(this.options.userAgent);
+        await page.setUserAgent(this.options.userAgent);
 
         this.pupBrowser = browser;
         this.pupPage = page;