fix: update path to CMK agent setup package for latest version (2.0.0)

tasks/install_checkmk_plugins.yml

 ---
 - name: CMK installieren
   yum:
-    name: "https://cmk.slub-dresden.de/slubmon/check_mk/agents/check-mk-agent-1.6.0p5-1.noarch.rpm"
+    name: "https://cmk.slub-dresden.de/slubmon/check_mk/agents/check-mk-agent-2.0.0p5-1.noarch.rpm"
     state: present
   when: ansible_os_family == "RedHat"