Bump checker-qual from 3.21.1 to 3.21.4 (#817)

Bumps [checker-qual](https://github.com/typetools/checker-framework) from 3.21.1 to 3.21.4.
- [Release notes](https://github.com/typetools/checker-framework/releases)
- [Changelog](https://github.com/typetools/checker-framework/blob/master/docs/CHANGELOG.md)
- [Commits](typetools/checker-framework@checker-framework-3.21.1...checker-framework-3.21.4)

---
updated-dependencies:
- dependency-name: org.checkerframework:checker-qual
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

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

Author: dependabot[bot]

typescript-generator-core/pom.xml

@@ -153,7 +153,7 @@
         <dependency>
             <groupId>org.checkerframework</groupId>
             <artifactId>checker-qual</artifactId>
-            <version>3.21.1</version>
+            <version>3.21.4</version>
             <scope>test</scope>
         </dependency>
         <!--test dependencies (additional data libraries)-->