Upgrade pitest-maven-plugin 1.17.4 -> 1.18.0 (#1538)

See:
- https://github.com/hcoles/pitest/releases/tag/1.18.0
- hcoles/pitest@1.17.4...1.18.0

pom.xml

@@ -1524,7 +1524,7 @@
                 <plugin>
                     <groupId>org.pitest</groupId>
                     <artifactId>pitest-maven</artifactId>
-                    <version>1.17.4</version>
+                    <version>1.18.0</version>
                     <configuration>
                         <excludedClasses>
                             <!-- AutoValue generated classes. -->