platform API: mark some elements with @ApiStatus.Internal annotation

Before they were marked as Experimental, but Internal is a more correct description here.

platform/util/src/com/intellij/openapi/util/JDOMUtil.java

@@ -279,7 +279,7 @@ public class JDOMUtil {
   /**
    * Internal use only.
    */
-  @ApiStatus.Experimental
+  @ApiStatus.Internal
   @NotNull
   public static Element load(@NotNull File file, @Nullable SafeJdomFactory factory) throws JDOMException, IOException {
     return loadUsingStaX(new BufferedReader(new InputStreamReader(new FileInputStream(file), StandardCharsets.UTF_8)), factory);
@@ -309,7 +309,7 @@ public class JDOMUtil {
   /**
    * Internal use only.
    */
-  @ApiStatus.Experimental
+  @ApiStatus.Internal
   @NotNull
   public static Element load(@NotNull InputStream stream, @Nullable SafeJdomFactory factory) throws JDOMException, IOException {
     return loadUsingStaX(new InputStreamReader(stream, StandardCharsets.UTF_8), factory);

platform/util/src/com/intellij/openapi/util/SafeJdomFactory.java

@@ -10,7 +10,7 @@ import org.jetbrains.annotations.Nullable;
 /**
  * Internal use only.
  */
-@ApiStatus.Experimental
+@ApiStatus.Internal
 public interface SafeJdomFactory {
   @NotNull
   Element element(@NotNull String name, @Nullable Namespace namespace);