stack/erp5: remove zabbix agent

stack/erp5/buildout.cfg

@@ -44,7 +44,6 @@ extends =
   ../../component/tesseract/buildout.cfg
   ../../component/w3m/buildout.cfg
   ../../component/poppler/buildout.cfg
-  ../../component/zabbix/buildout.cfg
   ../../component/sed/buildout.cfg
   ../../component/coreutils/buildout.cfg
   ../../component/grep/buildout.cfg
@@ -74,7 +73,6 @@ parts +=
   slapos-cookbook
   mroonga-mariadb
   tesseract
-  zabbix-agent
   .coveragerc
 
 # Buildoutish