[SPARK-53830] Exclude .idea directory from Spotless check

[dongjoon-hyun]

What changes were proposed in this pull request?

This PR aims to exclude .idea directory from Spotless check.

Why are the changes needed?

Currently, Spotless complains at IntelliJ files like the following. We should ignore these auto-generated files.

Execution failed for task ':spotlessMiscCheck'.
> The following files had format violations:
      .idea/codeStyles/Project.xml
          @@ -4,4 +4,4 @@
           ······<option·name="MULTILINE_STRING_CLOSING_QUOTES_ON_NEW_LINE"·value="true"·/>
           ····</ScalaCodeStyleSettings>
           ··</code_scheme>
          -</component>
          +</component>
      .idea/codeStyles/codeStyleConfig.xml
          @@ -2,4 +2,4 @@
           ··<state>
           ····<option·name="PREFERRED_PROJECT_CODE_STYLE"·value="Default"·/>
           ··</state>
          -</component>
          +</component>
      .idea/compiler.xml
          @@ -28,4 +28,4 @@
           ······<module·name="apache-spark-kubernetes-operator.spark-submission-worker.test"·options="-proc:full"·/>
           ····</option>
           ··</component>
          -</project>
          +</project>
      .idea/gradle.xml
          @@ -17,4 +17,4 @@
           ······</GradleProjectSettings>
           ····</option>
           ··</component>
          -</project>
          +</project>
      .idea/misc.xml
          @@ -2,4 +2,4 @@
           <project·version="4">
           ··<component·name="ExternalStorageConfigurationManager"·enabled="true"·/>
           ··<component·name="ProjectRootManager"·version="2"·languageLevel="JDK_X"·project-jdk-name="25"·project-jdk-type="JavaSDK"·/>
          -</project>
          +</project>
      .idea/vcs.xml
          @@ -3,4 +3,4 @@
           ··<component·name="VcsDirectoryMappings">
           ····<mapping·directory=""·vcs="Git"·/>
           ··</component>
          -</project>
          +</project>
      .idea/workspace.xml
          @@ -60,4 +60,4 @@
           ··<component·name="TypeScriptGeneratedFilesManager">
           ····<option·name="version"·value="3"·/>
           ··</component>
          -</project>
          +</project>
  Run './gradlew :spotlessApply' to fix these violations.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Manual review.

Was this patch authored or co-authored using generative AI tooling?

No.

[dongjoon-hyun]

Thank you always, @viirya ! Merged to main.