build(deps): bump checker from 4.2.3 to 4.3.1

Bumps `checker` from 4.2.3 to 4.3.1.

Updates `org.checkerframework:checker` from 4.2.3 to 4.3.1
- [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-4.2.3...checker-framework-4.3.1)

Updates `org.checkerframework:checker-qual` from 4.2.3 to 4.3.1
- [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-4.2.3...checker-framework-4.3.1)

---
updated-dependencies:
- dependency-name: org.checkerframework:checker
  dependency-version: 4.3.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.checkerframework:checker-qual
  dependency-version: 4.3.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

gradle/libs.versions.toml

@@ -1,7 +1,7 @@
 [versions]
 openapiparser = "2026.3-SNAPSHOT"
 
-checker = "4.2.3"
+checker = "4.3.1"
 
 [libraries]
 checker = { module = "org.checkerframework:checker", version.ref = "checker" }