Remove deprecated switch_role method

This is to remove the deprecated switch_role method from
rbac_utils module as it has been replaced by override_role
which is a superior way to manipulate the underlying role used
for querying API endpoints in Tempest.

Change-Id: Ibaffcd8cd0b62ad792b0ef5f9be4d33ec31e8c7a
diff --git a/releasenotes/notes/remove-deprecated-switch-role-148c9a5c6796857f.yaml b/releasenotes/notes/remove-deprecated-switch-role-148c9a5c6796857f.yaml
new file mode 100644
index 0000000..b303d09
--- /dev/null
+++ b/releasenotes/notes/remove-deprecated-switch-role-148c9a5c6796857f.yaml
@@ -0,0 +1,6 @@
+---
+upgrade:
+  - |
+    The ``switch_role`` method in ``rbac_utils`` module has been removed
+    because it is a clunky way of manipulating Tempest roles to achieve
+    RBAC testing. Use ``override_role`` instead.