Remove obsolete reference to rm-excluded-modes

C-h C-h v rm-excluded-modes shows:
rm-excluded-modes is a variable defined in ‘rich-minority.el’.
Its value is (" hl-p")

  This variable is an alias for ‘rm-blacklist’.
  This variable is obsolete since 0.1.1;
  use ‘rm-blacklist’ instead

README.org

@@ -100,7 +100,7 @@ Its main features include:
    The [[https://github.com/Malabarba/rich-minority][rich-minority]]
    package saves even more space. Select which minor modes you don't
    want to see listed by adding them to the variable
-   =rm-excluded-modes=, or even highlight the modes that are more
+   =rm-blacklist=, or even highlight the modes that are more
    important with the variable =rm-text-properties=. This will filter
    out the modes you don't care about and unclutter the modes list
    (mousing over the modes list still shows the full list).