ci: update all n1-standard-4 type runners to n2-standard-4 (#8340) (#8342)

(cherry picked from commit f08681f)

Co-authored-by: Panos Koutsovasilis <[email protected]>

Author: mergify[bot]

.buildkite/bk.integration.pipeline.yml

@@ -391,7 +391,7 @@ steps:
             limit: 1
         agents:
           provider: "gcp"
-          machineType: "n1-standard-4"
+          machineType: "n2-standard-4"
           image: "${IMAGE_UBUNTU_2404_X86_64}"
           diskSizeGb: 80
         matrix: