man: Document that Built-For-Profile is also included in .changes files

Missed in commit 7662e0937bb064a0754d12605d80a96a17e2aadf.

debian/changelog

@@ -15,6 +15,8 @@ dpkg (1.18.20) UNRELEASED; urgency=medium
       output gives meaningful results.
     - Disable the NFS-unsafe warning on Linux, as using flock() on NFS has
       been safe for some time now. Addresses: #677865 (on Linux)
+  * Documentation:
+    - Document the Built-For-Profile field in deb-changes(5).
 
   [ Updated scripts translations ]
   * German (Helge Kreutzmann).

man/deb-changes.man

@@ -125,6 +125,10 @@ This field denotes that the upload is a binary-only non-maintainer build.
 It originates from the \fBbinary\-only=yes\fP key/value from the changelog
 matadata entry.
 .TP
+.BI Built\-For\-Profiles: " profile-list"
+This field specifies a whitespace separated list of build profiles that
+this upload was built with.
+.TP
 .BR Changes: " (required)"
 .TQ
 .I " changelog-entries"