document why Artifact of is deprecated

The information was hidden in the changelog for 1.8.1

Signed-off-by: Pierre Tardy <[email protected]>

Author: tardyp

chapters/file-information.md

@@ -422,6 +422,8 @@ EXAMPLE 2 RDF: Property `spdx:copyrightText` in class `spdx:File`
 
 ## 8.9 Artifact of project name field (deprecated) <a name="8.9"></a>
 
+This field is deprecated since 1.8.4, as they can be replaced by a relationship to the more descriptive External Packages.
+
 ### 8.9.1 Description
 
 To indicate that a file has been derived from a specific project. The metadata for the artifact of project name field is shown in Table 44.
@@ -462,6 +464,8 @@ EXAMPLE 2 RDF: Property `spdx:artifactOf/doap:Project/doap:name`
 
 ## 8.10 Artifact of project homepage field (deprecated) <a name="8.10"></a>
 
+This field is deprecated since 1.8.4, as they can be replaced by a relationship to the more descriptive External Packages.
+
 ### 8.10.1 Description
 
 To indicate the location of the project from which the file has been derived. The metadata for the artifact of project homepage field is shown in Table 45.
@@ -500,6 +504,8 @@ EXAMPLE 2 RDF: `spdx:artifactOf/doap:Project/doap:homepage`
 
 ## 8.11 Artifact of project uniform resource identifier field (deprecated) <a name="8.11"></a>
 
+This field is deprecated since 1.8.4, as they can be replaced by a relationship to the more descriptive External Packages.
+
 ### 8.11.1 Description
 
 To provide a linkage to the project resource in the DOAP document and permit interoperability between the different formats supported. The metadata for the artifact of project uniform resource identifier field is shown in Table 46.