[SPARK-47455][BUILD] Fix resource leak during the initialization of `…

…scalaStyleOnCompileConfig` in `SparkBuild.scala`

### What changes were proposed in this pull request?
https://github.com/apache/spark/blob/e01ed0da22f24204fe23143032ff39be7f4b56af/project/SparkBuild.scala#L157-L173

`Source.fromFile(in)` opens a `BufferedSource` resource handle, but it does not close it, this pr fix this issue.

### Why are the changes needed?
Close resource after used.

### Does this PR introduce _any_ user-facing change?
No

### How was this patch tested?
Pass GitHub Actions

### Was this patch authored or co-authored using generative AI tooling?
No

Closes #45582 from LuciferYang/SPARK-47455.

Authored-by: yangjie01 <yangjie01@baidu.com>
Signed-off-by: yangjie01 <yangjie01@baidu.com>

project/SparkBuild.scala

@@ -160,16 +160,21 @@ object SparkBuild extends PomBuild {
     val replacements = Map(
       """customId="println" level="error"""" -> """customId="println" level="warn""""
     )
-    var contents = Source.fromFile(in).getLines.mkString("\n")
-    for ((k, v) <- replacements) {
-      require(contents.contains(k), s"Could not rewrite '$k' in original scalastyle config.")
-      contents = contents.replace(k, v)
-    }
-    new PrintWriter(out) {
-      write(contents)
-      close()
+    val source = Source.fromFile(in)
+    try {
+      var contents = source.getLines.mkString("\n")
+      for ((k, v) <- replacements) {
+        require(contents.contains(k), s"Could not rewrite '$k' in original scalastyle config.")
+        contents = contents.replace(k, v)
+      }
+      new PrintWriter(out) {
+        write(contents)
+        close()
+      }
+      out
+    } finally {
+      source.close()
     }
-    out
   }
 
   // Return a cached scalastyle task for a given configuration (usually Compile or Test)