AddressBookGuiTest#setup(): Remove redundant wait for stage to show
AddressBookGuiTest#setup(): Remove redundant wait for stage to show

AddressBookGuiTest#setup() waits for the stage to show up after executing
FxToolkit#showStage().

The wait is unncessary as FxToolkit#showStage() already blocks the
current thread until the stage is shown.

Let's remove the redundant wait.

damithc/addressbook-level4,CS2103R-Eugene-Peh/addressbook-level4,CS2103R-Eugene-Peh/addressbook-level4,damithc/addressbook-level4,damithc/addressbook-level4,se-edu/addressbook-level3,CS2103R-Eugene-Peh/addressbook-level4