added hints on deprecations/removals

Signed-off-by: Christian Dietrich <[email protected]>

xtext-website/_posts/releasenotes/2020-03-03-version-2-21-0.md

@@ -35,6 +35,9 @@ The Maven plugin has now two goals, `generate` and `testGenerate`. The new `test
 
 ## Deprecations
 
+* In `org.eclipse.xtext.ide` many of the LSP Services were changed in the protocol to use service specific parameters instead of `TextDocumentPositionParams`. We adapted the services to use the new parameter classes and marked the old onces as deprecated and to be removed with Xtext 2.22. If you have custom subclasses of the affected services please adopt your implementations.
+* We again encourage you to get rid of the old generator as we might have to remove it in 2020-06 / Xtext 2.22 - see/join [Xtext Issue #1669](https://github.com/eclipse/xtext/issues/1669).
+
 ## Credits
 
 The Xtext project is thankful for the dedication of each committer and contributor. This release has been made possible by the following persons (in order of the number of contributed commits to this release to [all repositories](https://github.com/eclipse/xtext#repositories) except [xtext-xtend](https://github.com/eclipse/xtext-xtend)):