Drone: update server images to use php 8

Signed-off-by: Álvaro Brey <alvaro.brey@nextcloud.com>

.drone.yml

@@ -29,7 +29,7 @@ steps:
 
 services:
   - name: server
-    image: ghcr.io/nextcloud/continuous-integration-server:latest # also change in updateScreenshots.sh
+    image: ghcr.io/nextcloud/continuous-integration-shallow-server:latest # also change in updateScreenshots.sh
     environment:
       EVAL: true
       SERVER_VERSION: 'stable25'
@@ -84,7 +84,7 @@ steps:
 
 services:
   - name: server
-    image: ghcr.io/nextcloud/continuous-integration-server:latest # also change in updateScreenshots.sh
+    image: ghcr.io/nextcloud/continuous-integration-shallow-server:latest # also change in updateScreenshots.sh
     environment:
       EVAL: true
     commands: