SLING-8888 Upgrade Karaf to 4.3.0

Use Karaf 4.3.0.RC1
diff --git a/pom.xml b/pom.xml
index 70acc47..f9e3f15 100644
--- a/pom.xml
+++ b/pom.xml
@@ -46,7 +46,7 @@
       <plugin>
         <groupId>org.apache.karaf.tooling</groupId>
         <artifactId>karaf-maven-plugin</artifactId>
-        <version>4.2.6</version>
+        <version>4.3.0.RC1</version>
         <extensions>true</extensions>
         <executions>
           <execution>