Fix "nullary method"

The terminology around 0-arity method is not used consistently, and not
clear so we should use the term used in 'Programming in Scala', which is
_empty-paren_ method.

If we insist on using the jargon, then _nilary_ is the term sometimes
used in scala/scala discussions.

Author: eed3si9n

incompat-30/auto-application/README.md

@@ -1,6 +1,6 @@
 ## Auto-application
 
-Auto-application is the syntax of calling a nullary method without passing an empty argument list.
+Auto-application is the syntax of calling an empty-paren method such as `def f(): Int` without passing an empty argument list.
 
 In Scala 3.0, when calling a method defined in Scala 3.0, this syntax is forbidden.