ISSUE_TEMPLATES: Remove note about forks from the Update Request form

The Package Request form no longer exists, so it makes no sense to mention it. We used to direct update requests to forks there, instead, users can now mention forks in the Additional Context section added in this commit.

Signed-off-by: Fernando Rodrigues <alpha@sigmasquadron.net>

.github/ISSUE_TEMPLATE/05_update_request.yml

@@ -22,9 +22,6 @@ body:
         > For instance, if you were filing a request against the out of date `hello` package, where the current version in Nixpkgs is 1.0.0, but the latest version upstream is 1.0.1, your title would be as follows:
         > `Update Request: hello 1.0.0 → 1.0.1`
 
-        > [!NOTE]
-        > If you are filing an update request to change a package's source to a fork, please file a new package request instead. Even if the original upstream is outdated, the fork should be considered a new package.
-
         ---
   - type: "dropdown"
     id: "version"
@@ -74,6 +71,13 @@ body:
       description: "If applicable, please link the upstream changelog for the latest version."
     validations:
       required: false
+  - type: "textarea"
+    id: "additional-context"
+    attributes:
+      label: "Additional context"
+      description: "Add any other context about the update here."
+    validations:
+      required: false
   - type: "textarea"
     id: "maintainers"
     attributes: