Specify maven-clean-plugin version

Sets the version to 3.4.1 in parent pom.
Having it unspecified causes the following warning:
```
[WARNING] Some problems were encountered while building the effective model for com.scylladb:java-driver-guava-shaded:jar:4.19.0.0-SNAPSHOT
[WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-clean-plugin is missing. @ line 97, column 15
[WARNING]
[WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
[WARNING]
[WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
[WARNING]
```

Author: Bouncheck

pom.xml

@@ -475,6 +475,11 @@
           <artifactId>maven-compiler-plugin</artifactId>
           <version>3.8.1</version>
         </plugin>
+        <plugin>
+          <groupId>org.apache.maven.plugins</groupId>
+          <artifactId>maven-clean-plugin</artifactId>
+          <version>3.4.1</version>
+        </plugin>
         <plugin>
           <groupId>com.coveo</groupId>
           <artifactId>fmt-maven-plugin</artifactId>