test/uninstall_spec: fix dependent cask handling

Library/Homebrew/test/uninstall_spec.rb

@@ -16,6 +16,8 @@ describe Homebrew::Uninstall do
   let(:dependent_cask) do
     Cask::CaskLoader.load(+<<-RUBY)
       cask "dependent_cask" do
+        version "1.0.0"
+
         url "c-1"
         depends_on formula: "dependency"
       end
@@ -38,6 +40,8 @@ describe Homebrew::Uninstall do
     ]
     tab.write
 
+    Cask::Caskroom.path.join("dependent_cask", dependent_cask.version).mkpath
+
     stub_formula_loader dependency
     stub_formula_loader dependent_formula
     stub_cask_loader dependent_cask