Add Pulsar 4.0.x to compatibility matrix doc

This commit adds 4.0.x Pulsar client to the compatibility
matrix doc.

Resolves #933

Author: onobc

spring-pulsar-docs/src/main/antora/modules/ROOT/pages/appendix/version-compatibility.adoc

@@ -8,7 +8,7 @@ The following is the compatibility matrix:
 | Spring for Apache Pulsar | Pulsar Client | Pulsar Reactive Client | Spring Boot | Java
 
 | 1.2.x
-| 3.3.x
+| 3.3.x / 4.0.x^**(*)**^
 | 0.6.x
 | 3.4.x
 | 17+
@@ -27,6 +27,14 @@ The following is the compatibility matrix:
 
 |===
 
+[NOTE]
+====
+^**(*)**^ The `3.3.x` Pulsar client is the default version specified by Spring for Apache Pulsar `1.2.x` and Spring Boot `3.4.x`.
+However, the `4.0.x` Pulsar client is compatible and will be the default version in the next minor releases (`1.3.x` and `3.5.x`, respectively).
+
+You can follow xref:appendix/override-boot-dependencies.adoc#override-boot-deps[these steps] to override the Pulsar client version.
+====
+
 [NOTE]
 ====
 If you are currently using Pulsar `2.11.x` you may notice that it is not present in the above matrix.