fix(web): make useProductChanges work as expected (#1526)

By mistake, #1483 introduced a
tiny bug in the `useProductChanges` query hook by checking the
`event.type` against an empty string instead of the exepected
`ProductChanged` event.

https://github.com/openSUSE/agama/pull/1483/files#diff-e671c06f4a1cefe3bef4af838681c780f2ba41356d44f72f5ce97be1b6eead66R172-R185

This PR fixes it for properly performs the software config query
invalidation.

web/src/queries/software.ts

@@ -188,7 +188,7 @@ const useProductChanges = () => {
     if (!client) return;
 
     return client.ws().onEvent((event) => {
-      if (event.type === "") {
+      if (event.type === "ProductChanged") {
         queryClient.invalidateQueries({ queryKey: ["software/config"] });
       }
     });