Bump guava from 29.0-jre to 30.0-jre in /core

Bumps [guava](https://github.com/google/guava) from 29.0-jre to 30.0-jre.
- [Release notes](https://github.com/google/guava/releases)
- [Commits](https://github.com/google/guava/commits)

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

core/build.gradle

@@ -5,7 +5,7 @@ buildscript {
 
     dependencies {
         // https://github.com/melix/japicmp-gradle-plugin/issues/36
-        classpath 'com.google.guava:guava:29.0-jre'
+        classpath 'com.google.guava:guava:30.0-jre'
     }
 }