add v18.x to mergify and dependabot (#3155)

Author: mpoke

.github/dependabot.yml

@@ -21,19 +21,18 @@ updates:
     directory: "/"
     schedule:
       interval: daily
-    target-branch: "release/v16.x"
+    target-branch: "release/v17.2.x"
     # Only allow automated security-related dependency updates on release branches.
     open-pull-requests-limit: 0
     labels:
       - dependencies
 
-
   - package-ecosystem: gomod
     directory: "/"
     schedule:
       interval: daily
-    target-branch: "release/v17.2.x"
+    target-branch: "release/v18.x"
     # Only allow automated security-related dependency updates on release branches.
     open-pull-requests-limit: 0
     labels:
-      - dependencies
+      - dependencies

.mergify.yml

@@ -24,20 +24,20 @@ pull_request_rules:
           {{ title }} (#{{ number }})
           {{ body }}
 
-  - name: Backport patches to the release/v16.x branch
+  - name: Backport patches to the release/v17.2.x branch
     conditions:
       - base=main
-      - label=A:backport/v16.x
+      - label=A:backport/v17.2.x
     actions:
       backport:
         branches:
-          - release/v16.x
+          - release/v17.2.x
 
-  - name: Backport patches to the release/v17.2.x branch
+  - name: Backport patches to the release/v18.x branch
     conditions:
       - base=main
-      - label=A:backport/v17.2.x
+      - label=A:backport/v18.x
     actions:
       backport:
         branches:
-          - release/v17.2.x
+          - release/v18.x