pom.xml: use htmlunit-driver 2.21 again.

Correction for ef59044 commit.

No functional changes.

Author: php-coder

pom.xml

@@ -381,7 +381,7 @@
 		<hibernate-validator.version>5.2.4.Final</hibernate-validator.version>
 
 		<!-- Redefine default value from spring-boot-dependencies (https://github.com/spring-projects/spring-boot/blob/v1.4.1.RELEASE/spring-boot-dependencies/pom.xml) -->
-		<htmlunit.version>2.20</htmlunit.version>
+		<htmlunit.version>2.21</htmlunit.version>
 
 		<jacoco.plugin.version>0.7.7.201606060606</jacoco.plugin.version>
 		<jasmine.plugin.version>2.2</jasmine.plugin.version>