Update field-mapping.asciidoc that Epoch format is not supported as dynamic date format (#98338)

* Update field-mapping.asciidoc that Epoch format is not supported as dynamic date format

Update field-mapping.asciidoc that Epoch format is not supported as dynamic date format

* Update docs/reference/mapping/dynamic/field-mapping.asciidoc

Co-authored-by: Abdon Pijpelink <abdon.pijpelink@elastic.co>

---------

Co-authored-by: Abdon Pijpelink <abdon.pijpelink@elastic.co>

docs/reference/mapping/dynamic/field-mapping.asciidoc

@@ -216,6 +216,11 @@ GET my-index-000001/_mapping
 --------------------------------------------------
 ====
 
+[NOTE]
+====
+Epoch formats (`epoch_millis` and `epoch_second`) are not supported as dynamic date formats.
+====
+
 [[numeric-detection]]
 ==== Numeric detection