Explicitly state polarion report authentication limitation (#3188)

spec/plans/report.fmf

@@ -87,6 +87,15 @@ description:
 
         __ https://github.com/RedHatQE/pylero
 
+        .. note::
+
+            For Polarion report to export correctly you need to
+            use password authentication, since exporting the
+            report happens through Polarion XUnit importer which
+            does not support using tokens. You can still
+            authenticate with token to only generate the report
+            using ``--no-upload`` argument.
+
         .. note::
 
             Your Polarion project might need a custom value format