Bump guava-testlib from 19.0 to 23.0 (iluwatar#1130)

Bumps [guava-testlib](https://github.com/google/guava) from 19.0 to 23.0.
- [Release notes](https://github.com/google/guava/releases)
- [Commits](google/guava@v19.0...v23.0)

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

Author: dependabot-preview[bot]

value-object/pom.xml

@@ -37,7 +37,7 @@
 		<dependency>
 			<groupId>com.google.guava</groupId>
 			<artifactId>guava-testlib</artifactId>
-			<version>19.0</version>
+			<version>23.0</version>
 			<scope>test</scope>
 		</dependency>
 		<dependency>