Shrink virtual disk size is supported using vCenter Converter, see: Growing, thinning, and shrinking virtual disks for VMware ESX and ESXi (1002019) | VMware KB
Shrinking
Virtual disk shrinking is supported when using VMware Converter converting source virtual machine as a machine source (not as virtual to virtual).
Note: You cannot shrink virtual disks using vmkfstools in ESXi as the hypervisor is not aware of the file system layout and cannot ensure a safe shrink operation.