updating nzbplanet.net api url to reflect recent change

src/NzbDrone.Core/Indexers/Newznab/Newznab.cs

@@ -49,7 +49,7 @@ namespace NzbDrone.Core.Indexers.Newznab
                 yield return GetDefinition("NZBCat", GetSettings("https://nzb.cat"));
                 yield return GetDefinition("NZBFinder.ws", GetSettings("https://www.nzbfinder.ws"));
                 yield return GetDefinition("NZBgeek", GetSettings("https://api.nzbgeek.info"));
-                yield return GetDefinition("nzbplanet.net", GetSettings("https://nzbplanet.net"));
+                yield return GetDefinition("nzbplanet.net", GetSettings("https://api.nzbplanet.net"));
                 yield return GetDefinition("Nzbs.org", GetSettings("http://nzbs.org", 5000));
                 yield return GetDefinition("OZnzb.com", GetSettings("https://api.oznzb.com"));
                 yield return GetDefinition("PFmonkey", GetSettings("https://www.pfmonkey.com"));