Bump org.mockito:mockito-core in /rascal-lsp in the upstream-libs group (#936)

Bumps the upstream-libs group in /rascal-lsp with 1 update: [org.mockito:mockito-core](https://github.com/mockito/mockito).


Updates `org.mockito:mockito-core` from 5.20.0 to 5.21.0
- [Release notes](https://github.com/mockito/mockito/releases)
- [Commits](mockito/mockito@v5.20.0...v5.21.0)

---
updated-dependencies:
- dependency-name: org.mockito:mockito-core
  dependency-version: 5.21.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
  dependency-group: upstream-libs
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

rascal-lsp/pom.xml

@@ -37,7 +37,7 @@
     <maven-surefire-plugin.version>3.5.4</maven-surefire-plugin.version>
     <log4j2.version>2.25.3</log4j2.version>
     <lsp4j.version>0.24.0</lsp4j.version>
-    <mockito.version>5.20.0</mockito.version>
+    <mockito.version>5.21.0</mockito.version>
     <sonar.organization>usethesource</sonar.organization>
     <sonar.host.url>https://sonarcloud.io</sonar.host.url>
   </properties>