Update image-builder-json.md

Bicep code for windows update customization was not working missing '

Author: fajterini

articles/virtual-machines/linux/image-builder-json.md

@@ -681,8 +681,8 @@ customize: [
     type: 'WindowsUpdate'
     searchCriteria: 'IsInstalled=0'
     filters: [
-      exclude:$_.Title -like '*Preview*''
-      include:$true'
+     'exclude:$_.Title -like \'*Preview*\''
+     'include:$true'
     ]
     updateLimit: 20
   }