refactor(ui5-duration-picker): make component private (#3530)

DurationPicker is now private component and will remain private until we refactor its API. It's a component that does not an equivalent in OpenUI5 and the required specs.

BREAKING CHANGE: DurationPicker is no longer supported, it may continue working, but it's not guarantee

Author: ilhan007

docs/Public Module Imports.md

@@ -38,7 +38,6 @@ For API documentation and samples, please check the [UI5 Web Components Playgrou
 | Date Range Picker        | `ui5-daterange-picker`   | `import "@ui5/webcomponents/dist/DateRangePicker.js";`     |
 | Date Time Picker         | `ui5-datetime-picker`    | `import "@ui5/webcomponents/dist/DateTimePicker.js";`      |
 | Dialog                   | `ui5-dialog`             | `import "@ui5/webcomponents/dist/Dialog.js";`              |
-| Duration Picker          | `ui5-duration-picker`    | `import "@ui5/webcomponents/dist/DurationPicker.js";`      |
 | File Uploader            | `ui5-file-uploader`      | `import "@ui5/webcomponents/dist/FileUploader.js";`        |
 | Icon                     | `ui5-icon`               | `import "@ui5/webcomponents/dist/Icon.js";`                |
 | Input                    | `ui5-input`              | `import "@ui5/webcomponents/dist/Input.js";`               |

packages/main/src/DurationPicker.js

@@ -7,7 +7,7 @@ import {
 } from "./generated/i18n/i18n-defaults.js";
 
 /**
- * @public
+ * @private
  */
 const metadata = {
 	tag: "ui5-duration-picker",
@@ -164,7 +164,7 @@ const pad = number => {
  * @alias sap.ui.webcomponents.main.DurationPicker
  * @extends TimePickerBase
  * @tagname ui5-duration-picker
- * @public
+ * @private
  */
 class DurationPicker extends TimePickerBase {
 	static get metadata() {