docs: Update version matrix

This is to address the below comment.

#2285 (comment)
Signed-off-by: Tam Mach <tam.mach@cilium.io>

README.md

@@ -43,9 +43,14 @@ binary releases.
 
 | Release                                                                | Maintained | Compatible Cilium Versions |
 |------------------------------------------------------------------------|------------|----------------------------|
-| [v0.15.23](https://github.com/cilium/cilium-cli/releases/tag/v0.15.23) | Yes        | Cilium 1.14 and newer      |
+| [v0.15.23](https://github.com/cilium/cilium-cli/releases/tag/v0.15.23) | Yes        | Cilium 1.15 and newer      |
+| [v0.15.22](https://github.com/cilium/cilium-cli/releases/tag/v0.15.22) | Yes        | Cilium 1.14 (*)            |
 | [v0.14.8](https://github.com/cilium/cilium-cli/releases/tag/v0.14.8)   | Yes        | Cilium 1.13                |
 
+Note: 
+- [v0.15.22](https://github.com/cilium/cilium-cli/releases/tag/v0.15.22) can
+  still be used for Cilium 1.15 and newer if Gateway API support is not enabled.
+
 ## Capabilities
 
 ### Install Cilium