Replace Openstack with OpenStack (#6413)

The official word is OpenStack, not Openstack as [1].
This replaces it with OpenStack in the docs.

[1]: https://www.openstack.org/

contrib/terraform/openstack/README.md

-# Kubernetes on Openstack with Terraform
+# Kubernetes on OpenStack with Terraform
 
 Provision a Kubernetes cluster with [Terraform](https://www.terraform.io) on
-Openstack.
+OpenStack.
 
 ## Status
 
-This will install a Kubernetes cluster on an Openstack Cloud. It should work on
+This will install a Kubernetes cluster on an OpenStack Cloud. It should work on
 most modern installs of OpenStack that support the basic services.
 
 ### Known compatible public clouds

docs/roadmap.md

@@ -13,7 +13,7 @@
 - [ ] Terraform to provision instances on:
   - [ ] GCE
   - [x] AWS (contrib/terraform/aws)
-  - [x] Openstack (contrib/terraform/openstack)
+  - [x] OpenStack (contrib/terraform/openstack)
   - [x] Packet
   - [ ] Digital Ocean
   - [ ] Azure