remove redundant Documentation tag

virtualization/virtualbox.md

@@ -1,6 +1,6 @@
 ---
 title: "virtualbox"
-tags: [ "Documentation", "System" ]
+tags: [ "System" ]
 ---
 # Setup
 

virtualization/xen/xen_basics.md

@@ -1,6 +1,6 @@
 ---
 title: "Xen Volume Management"
-tags: [ "Documentation", "xe", "virtualization", "volume" ]
+tags: [ "xe", "virtualization", "volume" ]
 ---
 # Make a local iso repository