Bump org.apache.tomcat.embed:tomcat-embed-core in /elda-testing-webapp

Bumps org.apache.tomcat.embed:tomcat-embed-core from 11.0.15 to 11.0.21.

---
updated-dependencies:
- dependency-name: org.apache.tomcat.embed:tomcat-embed-core
  dependency-version: 11.0.21
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

pom.xml

@@ -33,7 +33,7 @@
 
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <maven.build.timestamp.format>yyyy-MM-dd'T'HH:mm:ssZ</maven.build.timestamp.format>
-    <tomcat.version>11.0.15</tomcat.version>
+    <tomcat.version>11.0.21</tomcat.version>
   </properties>
 
   <build>