Bump xstream from 1.4.8 to 1.4.19 in /taverna-tavlang-tool

Bumps [xstream](https://github.com/x-stream/xstream) from 1.4.8 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>
diff --git a/taverna-tavlang-tool/pom.xml b/taverna-tavlang-tool/pom.xml
index 21c9520..ec81793 100644
--- a/taverna-tavlang-tool/pom.xml
+++ b/taverna-tavlang-tool/pom.xml
@@ -75,7 +75,7 @@
     <dependency>
       <groupId>com.thoughtworks.xstream</groupId>
       <artifactId>xstream</artifactId>
-      <version>1.4.8</version>
+      <version>1.4.19</version>
     </dependency>