Upgrade to Selenium HtmlUnit 2.24

Closes gh-7232

spring-boot-dependencies/pom.xml

@@ -88,7 +88,7 @@
 		<hibernate-validator.version>5.4.0.Final</hibernate-validator.version>
 		<hikaricp.version>2.5.1</hikaricp.version>
 		<hsqldb.version>2.3.3</hsqldb.version>
-		<htmlunit.version>2.21</htmlunit.version>
+		<htmlunit.version>2.24</htmlunit.version>
 		<httpasyncclient.version>4.1.3</httpasyncclient.version>
 		<httpclient.version>4.5.3</httpclient.version>
 		<httpcore.version>4.4.6</httpcore.version>
@@ -145,7 +145,7 @@
 		<rxjava-adapter.version>1.2.1</rxjava-adapter.version>
 		<rxjava2.version>2.0.6</rxjava2.version>
 		<selenium.version>3.1.0</selenium.version>
-		<selenium-htmlunit.version>2.21</selenium-htmlunit.version>
+		<selenium-htmlunit.version>2.24</selenium-htmlunit.version>
 		<sendgrid.version>2.2.2</sendgrid.version>
 		<servlet-api.version>3.1.0</servlet-api.version>
 		<simple-json.version>1.1.1</simple-json.version>