update docs for 5.8 with proper naming

Author: jdpleiness

docs/releases.mdx

@@ -12,6 +12,7 @@ Currently supported versions of Sourcegraph:
 
 | **Release**                     | **General Availability Date** | **Supported** | **Release Notes**                                        | **Install**                                          |
 |---------------------------------|-------------------------------|---------------|----------------------------------------------------------|------------------------------------------------------|
+| Sourcegraph 5 Release 8         | September 2024                | ✅             | [Notes](https://sourcegraph.com/docs/CHANGELOG#v580)     | [Install](https://sourcegraph.com/docs/admin/deploy) |
 | Sourcegraph 5 Release 7 Patch 1 | September 2024                | ✅             | [Notes](https://sourcegraph.com/docs/CHANGELOG#v572474)  | [Install](https://sourcegraph.com/docs/admin/deploy) |
 | Sourcegraph 5 Release 7         | September 2024                | ✅             | [Notes](https://sourcegraph.com/docs/CHANGELOG#v570)     | [Install](https://sourcegraph.com/docs/admin/deploy) |
 | Sourcegraph 5 Release 6 Patch 2 | August 2024                   | ✅             | [Notes](https://sourcegraph.com/docs/CHANGELOG#v562535)  | [Install](https://sourcegraph.com/docs/admin/deploy) |