Update Helm release oauth2-proxy to v10.4.2 (staging)

Author: govuk-ci

charts/kube-prometheus-stack-bootstrap/helm-versions/staging

@@ -1,3 +1,3 @@
 # $repo_url $chart_name: "$chart_version"
 https://prometheus-community.github.io/helm-charts kube-prometheus-stack: "82.18.0"
-https://oauth2-proxy.github.io/manifests oauth2-proxy: "10.3.0"
+https://oauth2-proxy.github.io/manifests oauth2-proxy: "10.4.2"