[setup-r-dependencies] fix docs for 'cache-version'

setup-r-dependencies/README.md

@@ -17,7 +17,7 @@ Inputs available
   not.
 - `cache-version` - default `1`. If you need to invalidate the existing
   cache pass any other number and a new cache will be used. Ignored if 
-  `cache: true`.
+  `cache: false`.
 - `dependencies` - default `'"all"'`. Types of dependencies to install. By
   default all direct dependencies of the current package are installed, and
   hard dependencies of these direct dependencies. See also the `needs` and