Apply suggestion from @Saviq

Author: Saviq

spread/sbuild/task.yaml

@@ -164,7 +164,7 @@ execute: |
 
     fi
 
-    if [ "${WAYLAND_EXPLORER}" = "true" ]; then
+    if [ "${WLPROBE}" = "true" ]; then
       # Regenerate the Wayland Explorer entry for Mir
       # Install Mir packages from the locally-built sbuild output in ../
       apt-get install --yes --no-install-recommends \