Update doc domain-modeling-tools for Java method call without parentheses

[cuzfrog]

Add parentheses when calling LocalDate.now to get an instance of LocalDate.

For a parameterless method, the recommended convention is that if no side effects, it should be without parentheses, so that def can be replaced by val/var.

In Scala3, the call site is enforced to match the method definition:

scala> def foo = 1
def foo: Int
scala> def bar() = 1
def bar(): Int    
scala> foo
val res3: Int = 1                  
scala> bar
-- [E100] Syntax Error

But this is not true when citing Java method:

scala> import java.time.*              
scala> val f = LocalDate.now // Questionable, side effect (reading external value)
val f: java.time.LocalDate = 2024-10-03                
scala> val t = LocalDate.now() // Good, explicitly mark the side effect performed
val t: java.time.LocalDate = 2024-10-03                  
scala> val f: () => LocalDate = LocalDate.now
val f: () => java.time.LocalDate = Lambda/0x000076984050d000@6c9151c1

This PR is to make the doc example follow the convention strictly.