Bump xstream from 1.4.6 to 1.4.19

Bumps [xstream](https://github.com/x-stream/xstream) from 1.4.6 to 1.4.19.
- [Release notes](https://github.com/x-stream/xstream/releases)
- [Commits](https://github.com/x-stream/xstream/commits)

---
updated-dependencies:
- dependency-name: com.thoughtworks.xstream:xstream
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

pom.xml

@@ -78,7 +78,7 @@
 		<!-- highchart export -->
 		<xercesImpl.version>2.7.1</xercesImpl.version>
 		<batik-codec.version>1.7</batik-codec.version>
-		<xstream.version>1.4.6</xstream.version>
+		<xstream.version>1.4.19</xstream.version>
 		<!-- jsoup HTML parser  -->
 		<jsoup.version>1.8.3</jsoup.version>