Add note about migrating records to value records

[Thiago Henrique Hupner]

I've read the updated JEP (https://openjdk.java.net/jeps/8277163) and one
thing
I think would be great to include that the migration of records to value
records is a breaking change.

There is already a section that specifies classes without public
constructors can be migrated to value classes without problems, but records
are often used with the implicit constructor, and that can go unnoticed
when migrating to value records.

Regards,

Thiago