[Misc] Upgrade TC to 1.19.8 and Selenium to 4.21.0

pom.xml

@@ -71,7 +71,7 @@
     <zookeeper.version>3.9.2</zookeeper.version>
 
     <!-- Versions of other software we need in our functional tests -->
-    <testcontainers.version>1.19.7</testcontainers.version>
+    <testcontainers.version>1.19.8</testcontainers.version>
     <!-- The LO version must point to the latest version from "Still" branch (LTS). When upgrading the version make
          sure the new version is available from https://download.documentfoundation.org/libreoffice/stable/
          Note: We don't need to exact version (e.g. 7.2.7.2) since the LTS is made available using a max of 2 dots

xwiki-platform-core/xwiki-platform-test/pom.xml

@@ -32,7 +32,7 @@
   <packaging>pom</packaging>
   <description>XWiki Platform - Test - Parent POM</description>
   <properties>
-    <selenium.version>4.20.0</selenium.version>
+    <selenium.version>4.21.0</selenium.version>
     <!-- Don't run backward-compatibility checks in test modules since we don't consider them as public APIs -->
     <xwiki.revapi.skip>true</xwiki.revapi.skip>
   </properties>