WebUI: migrate to fetch API

And away from mootools.

PR #22037.

src/webui/www/private/shareratio.html

@@ -100,19 +100,21 @@
                     return;
                 }
 
-                new Request({
-                    url: "api/v2/torrents/setShareLimits",
-                    method: "post",
-                    data: {
-                        hashes: hashesList.join("|"),
-                        ratioLimit: ratioLimitValue,
-                        seedingTimeLimit: seedingTimeLimitValue,
-                        inactiveSeedingTimeLimit: inactiveSeedingTimeLimitValue
-                    },
-                    onComplete: () => {
+                fetch("api/v2/torrents/setShareLimits", {
+                        method: "POST",
+                        body: new URLSearchParams({
+                            "hashes": hashesList.join("|"),
+                            "ratioLimit": ratioLimitValue,
+                            "seedingTimeLimit": seedingTimeLimitValue,
+                            "inactiveSeedingTimeLimit": inactiveSeedingTimeLimitValue
+                        })
+                    })
+                    .then(async (response) => {
+                        if (!response.ok)
+                            return;
+
                         window.parent.qBittorrent.Client.closeFrameWindow(window);
-                    }
-                }).send();
+                    });
             });
         });