JSIEVE-111 Upgrade apache parent pom version 18 -> 21
diff --git a/pom.xml b/pom.xml
index 8cd9390..148155c 100644
--- a/pom.xml
+++ b/pom.xml
@@ -23,7 +23,7 @@
     <parent>
         <groupId>org.apache</groupId>
         <artifactId>apache</artifactId>
-        <version>18</version>
+        <version>21</version>
         <relativePath />
     </parent>