[doc] update documentation for new mempoolfullrbf default

doc/policy/packages.md

@@ -38,7 +38,7 @@ The following rules are enforced for all packages:
 
 * Only limited package replacements are currently considered. (#28984)
 
-   - All direct conflicts must signal replacement (or the node must have `-mempoolfullrbf=1` set).
+   - If `-mempoolfullrbf=0` (the value is 1 by default), all direct conflicts must signal replacement.
 
    - Packages are 1-parent-1-child, with no in-mempool ancestors of the package.