Upgrade to Atomix 2.0.21

Change-Id: I9cf7ccf0ff6dc2a4caa737f6e69cea677f4b04fc
diff --git a/core/store/primitives/pom.xml b/core/store/primitives/pom.xml
index f20ed84..c1bf1a4 100644
--- a/core/store/primitives/pom.xml
+++ b/core/store/primitives/pom.xml
@@ -69,7 +69,7 @@
         <dependency>
             <groupId>io.atomix</groupId>
             <artifactId>atomix</artifactId>
-            <version>2.0.20</version>
+            <version>2.0.21</version>
         </dependency>
 
         <dependency>