Fix typo

MacOS -> macOS

Author: changeworld

includes/vpn-gateway-vwan-config-openvpn-mac.md

@@ -9,7 +9,7 @@
 ---
 
 > [!IMPORTANT]
-> Only MacOS 10.13 and above is supported with OpenVPN protocol.
+> Only macOS 10.13 and above is supported with OpenVPN protocol.
 
 [!INCLUDE [OpenVPN client version 2.6 not supported](./vpn-gateway-vwan-open-vpn-client-version-unsupported.md)]