Update core-types.asciidoc
Update core-types.asciidoc

Updated accessing fields section.  Currently, the deprecation message is placed in the beginning of this section and can be confusing since the path notation (eg. name.raw) for multi fields defined in `fields` is not deprecated.  The changes attempt to clarify the deprecation to be specific to the `path option` used to set up custom _all fields in the past.
fubuki/elasticsearch,aparo/elasticsearch,aparo/elasticsearch,fubuki/elasticsearch,aparo/elasticsearch,aparo/elasticsearch,aparo/elasticsearch,fubuki/elasticsearch,fubuki/elasticsearch,aparo/elasticsearch,fubuki/elasticsearch,fubuki/elasticsearch