Update checklists for Deprecation issue template

Adds more checkboxes to the Deprecation issue template to
track the progress of the deprecation and removal of features.

https://gitlab.com/gitlab-org/gitlab/-/issues/345974

.gitlab/issue_templates/Deprecations.md

@@ -34,15 +34,33 @@ Which tier is this feature available in?
 * Ultimate
 -->
 
-### Checklist
+### Checklists
 
-- [ ] @mention your stage's stable counterparts on this issue. For example, Customer Support, Customer Success (Technical Account Manager), Product Marketing Manager.
+**Labels**
+
+- [ ] This issue is labeled ~deprecation, and with the relevant `~devops::`, `~group::`, and `~Category:` labels.
+- [ ] This issue is labeled  ~"breaking change" if the removal of the deprecated item will be a [breaking change](https://about.gitlab.com/handbook/product/gitlab-the-product/#examples-of-breaking-changes).
+
+**Timeline**
+
+Please add links to the relevant merge requests.
+
+- As soon as possible, but no later than the third milestone preceding the major release (for example, given the following release schedule: `14.8, 14.9, 14.10, 15.0` – `14.8` is the third milestone preceding the major release):
+    - [ ] A [deprecation entry](https://about.gitlab.com/handbook/marketing/blog/release-posts/#creating-a-deprecation-entry) has been created so the deprecation will appear in release posts and on the [general deprecation page](https://docs.gitlab.com/ee/update/deprecations).
+    - [ ] Documentation has been updated to add a note about the [end-of-life](https://docs.gitlab.com/ee/development/documentation/styleguide/#end-of-life-for-features-or-products) and to mark the feature as [deprecated](https://docs.gitlab.com/ee/development/documentation/styleguide/#deprecated-features).
+- [ ] On or before the major milestone: A [removal entry](https://about.gitlab.com/handbook/marketing/blog/release-posts/#removals) has been created so the removal will appear on the [removals by milestones](https://docs.gitlab.com/ee/update/removals) page and be announced in the release post.
+- On the major milestone:
+    - [ ] The deprecated item has been removed.
+    - [ ] If the removal of the deprecated item is a [breaking change](https://about.gitlab.com/handbook/product/gitlab-the-product/#examples-of-breaking-changes), the merge request is labeled ~"breaking change".
+
+**Mentions**
+
+- [ ] Your stage's stable counterparts have been `@mentioned`  on this issue. For example, Customer Support, Customer Success (Technical Account Manager), Product Marketing Manager.
   - To see who the stable counterparts are for a product team visit [product categories](https://about.gitlab.com/handbook/product/categories/)
        - If there is no stable counterpart listed for Sales/CS please mention `@timtams`
        - If there is no stable counterpart listed for Support please mention `@gitlab-com/support/managers`
        - If there is no stable counterpart listed for Marketing please mention `@cfoster3`
-
-- [ ] `@mention` your GPM so that they are aware of planned deprecations. The goal is to have reviews happen at least two releases before the final removal of the feature or introduction of a breaking change.
+- [ ] Your GPM has been `@mentioned` so that they are aware of planned deprecations. The goal is to have reviews happen at least two releases before the final removal of the feature or introduction of a breaking change.
 
 ### Deprecation Milestone
 
@@ -75,6 +93,6 @@ Use the following resources to find the appropriate labels:
 /label  ~"GitLab Free" ~"GitLab Premium" ~"GitLab Ultimate"
 
 <!-- Identifies that this Issue is related to deprecating a feature -->
-/label ~"type::deprecation"
+/label ~"deprecation"
 
 <!-- Add the ~"breaking change" label to this issue if necessary -->