Update pmd-core/src/main/java/net/sourceforge/pmd/util/IOUtil.java

Co-authored-by: Clément Fournier <clement.fournier76@gmail.com>

pmd-core/src/main/java/net/sourceforge/pmd/util/IOUtil.java

@@ -180,6 +180,13 @@ public final class IOUtil {
         }
     }
 
+
+    // The following methods are taken from Apache Commons IO.
+    // The dependency was removed from PMD 6 because it had a security issue,
+    // and upgrading was not possible without upgrading to Java 8.
+    // See https://github.com/pmd/pmd/pull/3968
+    // TODO PMD 7: consider bringing back commons-io and cleaning this class up.
+
     public static void closeQuietly(Closeable closeable) {
         try {
             closeable.close();