elk.feature: Added missing 0.8.1 version.

Signed-off-by: Soeren Domroes <sdo@informatik.uni-kiel.de>

Author: soerendomroes

features/org.eclipse.elk.feature/feature.xml

@@ -11,7 +11,7 @@
 <feature
       id="org.eclipse.elk.feature"
       label="Eclipse Layout Kernel (Incubation) - Core Components"
-      version="0.9.0.qualifier"
+      version="0.8.1"
       provider-name="Eclipse Layout Kernel"
       plugin="org.eclipse.elk.core">