Remove confusing statement

Previously, you couldn't mix epics and issues in
the ordering of the epic tree, but it's no longer
the case.

The sentence "Issues and child epics cannot be
intermingled." is no longer true.

doc/user/group/epics/manage_epics.md

@@ -33,7 +33,8 @@ You will be taken to the new epic where can edit the following details:
 
 An epic's page contains the following tabs:
 
-- **Epics and Issues**: epics and issues added to this epic. Child epics, and their issues, are shown in a tree view.
+- **Epics and Issues**: epics and issues added to this epic. Child epics, and their issues, are
+  shown in a tree view.
   - Click the <kbd>></kbd> beside a parent epic to reveal the child epics and issues.
   - Hover over the total counts to see a breakdown of open and closed items.
 - **Roadmap**: a roadmap view of child epics which have start and due dates.
@@ -137,8 +138,8 @@ confidential** checkbox.
 
 ### Enable Confidential Epics **(PREMIUM ONLY)**
 
-The Confidential Epics feature is under development and not ready for production use. It's deployed behind a
-feature flag that is **disabled by default**.
+The Confidential Epics feature is under development and not ready for production use.
+It's deployed behind a feature flag that is **disabled by default**.
 [GitLab administrators with access to the GitLab Rails console](../../../administration/feature_flags.md)
 can enable it for your instance.
 
@@ -208,7 +209,7 @@ To remove an issue from an epic:
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/9367) in GitLab 12.5.
 
 New issues are added to the top of their list in the **Epics and Issues** tab.
-You can reorder the list of issues. Issues and child epics cannot be intermingled.
+You can reorder the list of issues.
 
 To reorder issues assigned to an epic:
 
@@ -225,7 +226,7 @@ To reorder child epics assigned to an epic:
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/33039) in [GitLab Ultimate](https://about.gitlab.com/pricing/) 13.0.
 
 New issues are added to the top of their list in the **Epics and Issues**
-tab. You can move issues from one epic to another. Issues and child epics cannot be intermingled.
+tab. You can move issues from one epic to another.
 
 To move an issue to another epic:
 
@@ -235,7 +236,7 @@ To move an issue to another epic:
 ### Promote an issue to an epic
 
 > - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/3777) in [GitLab Ultimate](https://about.gitlab.com/pricing/) 11.6.
-> - In [GitLab 12.8](https://gitlab.com/gitlab-org/gitlab/-/issues/37081), it was moved to the Premium tier.
+> - [Moved](https://gitlab.com/gitlab-org/gitlab/-/issues/37081) to [GitLab Premium](https://about.gitlab.com/pricing/) in 12.8.
 
 If you have [permissions](../../permissions.md) to close an issue and create an
 epic in the parent group, you can promote an issue to an epic with the `/promote`
@@ -266,7 +267,8 @@ To add a child epic to an epic:
 1. Click **Add an epic**.
 1. Identify the epic to be added, using either of the following methods:
    - Paste the link of the epic.
-   - Search for the desired issue by entering part of the epic's title, then selecting the desired match (introduced in [GitLab 12.5](https://gitlab.com/gitlab-org/gitlab/-/issues/9126)).
+   - Search for the desired issue by entering part of the epic's title, then selecting the desired
+     match (introduced in [GitLab 12.5](https://gitlab.com/gitlab-org/gitlab/-/issues/9126)).
 
    If there are multiple epics to be added, press <kbd>Spacebar</kbd> and repeat this step.
 1. Click **Add**.
@@ -290,7 +292,7 @@ To move child epics to another epic:
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/9367) in GitLab 12.5.
 
 New child epics are added to the top of their list in the **Epics and Issues** tab.
-You can reorder the list of child epics. Issues and child epics cannot be intermingled.
+You can reorder the list of child epics.
 
 To reorder child epics assigned to an epic: