Bump openstacksdk from 3.1.0 to 4.0.0 in /.github/workflows

Bumps [openstacksdk](https://docs.openstack.org/openstacksdk/) from 3.1.0 to 4.0.0.

---
updated-dependencies:
- dependency-name: openstacksdk
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/requirements.in

@@ -1 +1 @@
-openstacksdk == 3.1.0
+openstacksdk == 4.0.0

.github/workflows/requirements.txt

@@ -30,7 +30,7 @@ keystoneauth1==5.6.0
     # via openstacksdk
 netifaces==0.11.0
     # via openstacksdk
-openstacksdk==3.1.0
+openstacksdk==4.0.0
     # via -r requirements.in
 os-service-types==1.7.0
     # via