Add a missed PR and compat note to the RN

Thanks @ffesti for noticing!

wiki/Releases/4.20.0.md

@@ -33,6 +33,7 @@ Last update: 2024-04-05
 * Packaging: Add support for declarative buildsystem ([#2774](https://github.com/rpm-software-management/rpm/pull/2774))
 * Packaging: Add support for spec local file attributes and generators ([#2911](https://github.com/rpm-software-management/rpm/pull/2911))
 * Packaging: Add support for sysusers group membership lines ([#2990](https://github.com/rpm-software-management/rpm/pull/2990))
+* Packaging: Allow comments after conditionals ([#2996](https://github.com/rpm-software-management/rpm/pull/2996))
 * Packaging: Allow to specify a default for bcond features in a macro file ([#2405](https://github.com/rpm-software-management/rpm/pull/2405))
 * Packaging: Expose build time to package build scriptlets via `$RPM_BUILD_TIME` ([#2933](https://github.com/rpm-software-management/rpm/pull/2933))
 * Packaging: Implement prepend and append modes for all our normal build scriptlets ([#2728](https://github.com/rpm-software-management/rpm/pull/2728))
@@ -55,6 +56,7 @@ Last update: 2024-04-05
 * Generators: Remove perl dependency generators from the repo ([#2947](https://github.com/rpm-software-management/rpm/pull/2947))
 
 ### Deprecations
+* Packaging: Allow comments after conditionals ([#2996](https://github.com/rpm-software-management/rpm/pull/2996))
 * Split the internal OpenPGP parser to a separate repository ([#2986](https://github.com/rpm-software-management/rpm/pull/2986))
 
 ### Fixes
@@ -84,5 +86,7 @@ Last update: 2024-04-05
 ## Compatibility notes
 * The `%patchN` macro syntax (where `N` is a patch number) is now obsolete and
   will produce a build error.  Use `%patch N` (or `%patch -P N`) instead.
+* Comments after SPEC conditionals are now valid syntax (and won't cause a
+  warning), any other text that doesn't start with a `#` is now an error.
 * The `rpm2cpio(8)` utility has been [removed](https://github.com/rpm-software-management/rpm/pull/2758) in favor of `rpm2archive(8)`.
 * Python 3.7 and OpenSSL 3.0 are now the minimum build requirements.