[8.x] [8.17][Main] Update .mergify.yml (backport #5958) (#5961)

* Update .mergify.yml (#5958)

Adds 8.17.0 to mergify and updates 8.16.

(cherry picked from commit a14abe6)

# Conflicts:
#	.mergify.yml

* Merge conflicts

---------

Co-authored-by: Janeen Mikell Roberts <57149392+jmikell821@users.noreply.github.com>
Co-authored-by: lcawl <lcawley@elastic.co>

.mergify.yml

@@ -13,6 +13,34 @@ pull_request_rules:
             git merge upstream/{{base}}
             git push upstream {{head}}
             ```
+  - name: backport patches to 8.17 branch
+    conditions:
+      - merged
+      - base=main
+      - label=v8.17.0
+    actions:
+      backport:
+        assignees:
+          - "{{ author }}"
+        branches:
+          - "8.x"
+        title: "[{{ destination_branch }}] {{ title }} (backport #{{ number }})"
+        labels:
+          - backport
+  - name: backport patches to 8.16 branch
+    conditions:
+      - merged
+      - base=main
+      - label=v8.16.0
+    actions:
+      backport:
+        assignees:
+          - "{{ author }}"
+        branches:
+          - "8.16"
+        title: "[{{ destination_branch }}] {{ title }} (backport #{{ number }})"
+        labels:
+          - backport
   - name: backport patches to 8.15 branch
     conditions:
       - merged