Invert usage of manager.isExpired()

When it's expired it means, that the app should get the data. Meaning it should not abort prematurely by returning null.

Co-authored-by: Tobias Groza <TobiGr@users.noreply.github.com>

app/src/main/java/org/schabi/newpipe/CheckForNewAppVersion.java

@@ -180,7 +180,7 @@ public final class CheckForNewAppVersion {
         }
 
         final long expiry = prefs.getLong(app.getString(R.string.update_expiry_key), 0);
-        if (manager.isExpired(expiry)) {
+        if (!manager.isExpired(expiry)) {
             return null;
         }