refactor: default clipboard image base64 to JPG instead of PNG

Hardcoding this is already far from ideal. We should at least use the
same type that's later used in desktop before sending images to
status-go, **before** this gets fixed properly.

The next step will be to detect codecs and use them them dynamically.

vendor/DOtherSide/lib/src/Status/QClipboardProxy.cpp

@@ -54,8 +54,8 @@ QString QClipboardProxy::imageBase64() const
     const auto img = image();
     QByteArray byteArray;
     QBuffer buffer(&byteArray);
-    img.save(&buffer, "PNG"); // writes the image in PNG format inside the buffer
-    return QStringLiteral("data:image/png;base64,") + byteArray.toBase64();
+    img.save(&buffer, "JPG");
+    return QStringLiteral("data:image/jpeg;base64,") + byteArray.toBase64();
 }
 
 bool QClipboardProxy::hasUrls() const