Update Due dates page with minor edits

Revise Due dates page with several minor edits.

doc/user/project/issues/due_dates.md

@@ -4,13 +4,9 @@ group: Project Management
 info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
 ---
 
-# Due dates
+# Due dates **(FREE)**
 
-> [Introduced](https://gitlab.com/gitlab-org/gitlab-foss/-/merge_requests/3614) in GitLab 8.7.
-
-Please read through the [GitLab Issue Documentation](index.md) for an overview on GitLab Issues.
-
-Due dates can be used in issues to keep track of deadlines and make sure features are
+Due dates can be used in [issues](index.md) to keep track of deadlines and make sure features are
 shipped on time. Users need at least [Reporter permissions](../../permissions.md)
 to be able to edit the due date. All users with permission to view
 the issue can view the due date.
@@ -24,11 +20,11 @@ the user setting the due date.
 
 ![Create a due date](img/due_dates_create.png)
 
-You can also set a due date via the issue sidebar. Expand the
-sidebar and click **Edit** to pick a due date or remove the existing one.
+You can also set a due date by using the issue sidebar. Expand the
+sidebar and select **Edit** to pick a due date or remove the existing one.
 Changes are saved immediately.
 
-![Edit a due date via the sidebar](img/due_dates_edit_sidebar.png)
+![Edit a due date with the sidebar](img/due_dates_edit_sidebar.png)
 
 The last way to set a due date is by using [quick actions](../quick_actions.md), directly in an issue's description or comment:
 
@@ -52,9 +48,9 @@ of the issue. Like the due date, the "day before the due date" is determined by
 server's timezone.
 
 Issues with due dates can also be exported as an iCalendar feed. The URL of the
-feed can be added to calendar applications. The feed is accessible by clicking
-on the **Subscribe to calendar** button on the following pages:
+feed can be added to calendar applications. The feed is accessible by selecting
+the **Subscribe to calendar** button on the following pages:
 
-- on the **Assigned Issues** page that is linked on the right-hand side of the GitLab header
-- on the **Project Issues** page
-- on the **Group Issues** page
+- The **Assigned Issues** page linked on the right side of the GitLab header
+- The **Project Issues** page
+- The **Group Issues** page