Fix cluster tiers in Limitations section (#594)

* fix cluster tiers in considerations

* revert section name

* wording

Author: zach-carr

source/scheduled-reports.txt

@@ -45,11 +45,11 @@ have:
 Limitations
 ~~~~~~~~~~~
 
-- For free and shared tier clusters (``M0``, ``M2``, and ``M5``), you 
-  can create one scheduled report per project.
+- For ``M0`` {+clusters+}, you can create one scheduled report per 
+  project.
 
-- For paid-tier clusters (``M10+``), you can create up to 100 scheduled 
-  reports per project.
+- For ``M2`` and higher tier {+clusters+}, you can create up to 100 
+  scheduled reports per project.
 
 - At this time, scheduled reports can only be sent by email.