Use core-windows-2022 image instead of unmaintained ci-windows-2022 (#97

)

The image family `ci-windows-2022` has been unmaintained for a while and
has been replaced by `core-windows-2022`. This PR updates them to this
instead.

Related to [incident
505.](https://elastic.slack.com/archives/C078RND5G5C)

.buildkite/pipeline.yml

@@ -4,7 +4,7 @@ env:
   SETUP_GVM_VERSION: 'v0.5.0'
   GO_VERSION_CHOCO: "1.20.5"
   LINUX_AGENT_IMAGE: "golang:${GO_VERSION}"
-  WINDOWS_AGENT_IMAGE: "family/ci-windows-2022"
+  WINDOWS_AGENT_IMAGE: "family/core-windows-2022"
 
 steps:
   - label: ":golangci-lint: Lint"