Update --task.yaml (#29920)

Updates the "Task" issue template

- Removes the required input of "Have you searched for similar issues?"
- Makes the tasks body a required input


Removing the "Have you searched for similar issues?" because this
template is used mostly internally for incremental issues towards a
project / epic and not used by the community

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Documentation**
- Updated the issue template by removing the checkbox for checking
existing issues.
- Modified the 'SubTasks' field from a text area to a mandatory checkbox
list in the issue template.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

.github/ISSUE_TEMPLATE/--task.yaml

@@ -3,18 +3,11 @@ description: Create a task for the team to work on
 title: "[Task]: "
 labels: [Task]
 body:
-- type: checkboxes
-  attributes:
-    label: Is there an existing issue for this?
-    description: Please search to see if an issue related to this already exists.
-    options:
-    - label: I have searched the existing issues
-      required: true
 - type: textarea
   attributes:
     label: SubTasks 
     placeholder: |
-      - Sub Task 1
+      - [ ] Sub Task 1
-      - Sub Task 2
+      - [ ] Sub Task 2
   validations:
-    required: false
+    required: true