fix(docker): correct stale image tag in 8.0.0 README

The 8.0.0 dir's compose example referenced openemr/openemr:7.0.5 (a
copy-paste predating the 8.0.0 tag). Now that per-version dirs are
excluded from rotation, this stale tag can no longer be auto-corrected,
so fix it to match the dir (matching the 8.1.0/8.1.1/7.0.4 convention).

Assisted-by: Claude Code

Author: kojiromike

docker/openemr/8.0.0/README.md

@@ -30,7 +30,7 @@ services:
       MYSQL_ROOT_PASSWORD: root
   openemr:
     restart: always
-    image: openemr/openemr:7.0.5
+    image: openemr/openemr:8.0.0
     ports:
     - 80:80
     - 443:443