Update README.md (#132)

With the new containerized release to stage environment,  Stage uses a single branch approach so both stage-stable and stage-beta envs are ran off of master.

README.md

@@ -29,7 +29,7 @@ Any push to the following branches will trigger a build in [vuln4shift-frontend-
 | Push to branch in this repo  | Updated branch in build repo  | Environment       | Available at
 | :--------------------------- | :---------------------------- | :---------------- | :-----------
 | master                       | stage-beta                    | stage beta        | https://console.stage.redhat.com/preview
-| stage-stable                 | stage-stable                  | stage stable      | https://console.stage.redhat.com
+| master                 | stage-stable                  | stage stable      | https://console.stage.redhat.com
 | prod-beta                    | prod-beta                     | production beta   | https://console.redhat.com/preview
 | prod-stable                  | prod-stable                   | production stable | https://console.redhat.com