Upgrade Checker Framework Annotations 3.30.0 -> 3.31.0 (#502)

See:
- https://github.com/typetools/checker-framework/releases/tag/checker-framework-3.31.0
- typetools/checker-framework@checker-framework-3.30.0...checker-framework-3.31.0

pom.xml

@@ -356,7 +356,7 @@
             <dependency>
                 <groupId>org.checkerframework</groupId>
                 <artifactId>checker-qual</artifactId>
-                <version>3.30.0</version>
+                <version>3.31.0</version>
             </dependency>
             <dependency>
                 <groupId>org.hamcrest</groupId>