[KYUUBI #6820] Explicitly disable attach-scaladocs for pure Java modules

```
export JAVA_HOME=/path/of/openjdk-17
build/mvn clean install -DskipTests -Dmaven.scaladoc.skip=false
```

```
[INFO] --- scala-maven-plugin:4.9.2:doc-jar (attach-scaladocs)  kyuubi-server-plugin ---
[INFO] compiler plugin: BasicArtifact(com.github.ghik,silencer-plugin_2.12.20,1.7.19,null)
error: fatal error: object scala in compiler mirror not found.
```

- [x] Bugfix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing functionality to change)

Successfully run the build command
```
export JAVA_HOME=/path/of/openjdk-17
build/mvn clean install -DskipTests -Dmaven.scaladoc.skip=false
```

---

- [x] This patch was not authored or co-authored using [Generative Tooling](https://www.apache.org/legal/generative-tooling.html)

**Be nice. Be informative.**

Closes #6820 from pan3793/scaladoc.

Closes #6820

f5cee3429 [Cheng Pan] Explicitly disable attach-scaladocs for pure Java modules

Authored-by: Cheng Pan <chengpan@apache.org>
Signed-off-by: Cheng Pan <chengpan@apache.org>
(cherry picked from commit 4b506f4cb9)
Signed-off-by: Cheng Pan <chengpan@apache.org>

extensions/server/kyuubi-server-plugin/pom.xml

@@ -35,9 +35,12 @@
             <plugin>
                 <groupId>net.alchim31.maven</groupId>
                 <artifactId>scala-maven-plugin</artifactId>
-                <configuration>
-                    <skip>true</skip>
-                </configuration>
+                <executions>
+                    <execution>
+                        <id>attach-scaladocs</id>
+                        <phase>none</phase>
+                    </execution>
+                </executions>
             </plugin>
         </plugins>
     </build>