Rename master to main

Author: ikarldasan

release-tools/SIDECAR_RELEASE_PROCESS.md

@@ -89,7 +89,7 @@ naming convention `<hostpath-deployment-version>-on-<kubernetes-version>`.
 1. Check [image build status](https://k8s-testgrid.appspot.com/sig-storage-image-build).
 1. Promote images from k8s-staging-sig-storage to k8s.gcr.io/sig-storage. From
    the [k8s image
-   repo](https://github.com/kubernetes/k8s.io/tree/master/k8s.gcr.io/images/k8s-staging-sig-storage),
+   repo](https://github.com/kubernetes/k8s.io/tree/main/k8s.gcr.io/images/k8s-staging-sig-storage),
    run `./generate.sh > images.yaml`, and send a PR with the updated images.
    Once merged, the image promoter will copy the images from staging to prod.
 1. Update [kubernetes-csi/docs](https://github.com/kubernetes-csi/docs) sidecar