Update plotlystream_demo.m

Author: jackparmer

plotly/plotlystream_aux/plotlystream_demo.m

@@ -5,7 +5,7 @@
 catch
     fprintf(['\nOops - No stream_keys found! please run: >>saveplotlycredentials(',...
         ' ''username'',''api_key'',''stream_key).'' \n',...
-        'Your stream key(s) can be found online at: https://plot.ly or contact [email protected]',...
+        'Your stream key(s) can be found online at: https://plot.ly or post a topic on https://community.plotly.com/c/api/matlab/',...
         'for more information.\n\n']);
     return
 end