fix: allow overriding _getInputElement()

This was accidentally marked as `@private` for TS defs generation but it was originally correctly intended as `@protected`. This is overridden in vaadin-date-time-picker. See: 8730119#diff-f47a6ede93b6671ca3a69fb260ffacfc

src/vaadin-time-picker.html

@@ -645,7 +645,7 @@
           return TimePickerElement.properties.i18n.value().parseTime(text);
         }
 
-        /** @private */
+        /** @protected */
         _getInputElement() {
           return this.shadowRoot.querySelector('vaadin-time-picker-text-field');
         }