doc: Update features removal schedule

- The -u, --udeb dpkg-scanpackages options got removed, state that.
- Remove the entry about obsolete fields, as these need to be preserved
  for backward compatibility, they are part of the external interface
  to be able to handle ancient binary packages.

debian/changelog

@@ -20,6 +20,11 @@ dpkg (1.17.21) UNRELEASED; urgency=low
     to process triggers for packages that are not yet ready in the first
     dependtry, but which might be a bit later on, without wrongly detecting
     avoidable and bogus trigger cycles. Closes: #766557
+  * Update features removal schedule:
+    - The -u, --udeb dpkg-scanpackages options got removed, state that.
+    - Remove the entry about obsolete fields, as these need to be preserved
+      for backward compatibility, they are part of the external interface to
+      be able to handle ancient binary packages.
 
   [ Updated programs translations ]
   * Catalan (Guillem Jover).

doc/README.feature-removal-schedule

@@ -18,15 +18,6 @@ Why:
  The semantics of Source-Version are missleading when applied to binNMUs.
  Should switch to use binary:Version or source:Version substvars.
 
-What: Revision, Package-Revision, Package_Revision, Class, Recommended,
-      Optional (field)
-Status: obsolete
-When: 1.15.x
-Warning: program
-Why:
- These fields have been superseded by either other fields with better names
- or values in other fields.
-
 What: --print-installation-architecture (dpkg option)
 Status: obsolete
 When: 1.15.x
@@ -149,7 +140,7 @@ Why:
  rely on some of its features.
 
 What: -u, --udeb (dpkg-scanpackages option)
-Status: deprecated
+Status: removed
 When: 1.16.4
 Warning: program
 Why: