Use short-style lambdas.

Library/Homebrew/cask/test/cask/artifact/alt_target_test.rb

@@ -5,7 +5,7 @@ describe Hbc::Artifact::App do
     let(:cask) { Hbc.load("with-alt-target") }
 
     let(:install_phase) {
-      lambda { Hbc::Artifact::App.new(cask).install_phase }
+      -> { Hbc::Artifact::App.new(cask).install_phase }
     }
 
     let(:source_path) { cask.staged_path.join("Caffeine.app") }

Library/Homebrew/cask/test/cask/artifact/app_test.rb

@@ -9,13 +9,8 @@ describe Hbc::Artifact::App do
   let(:source_path) { cask.staged_path.join("Caffeine.app") }
   let(:target_path) { Hbc.appdir.join("Caffeine.app") }
 
-  let(:install_phase) {
-    lambda { app.install_phase }
-  }
-
-  let(:uninstall_phase) {
-    lambda { app.uninstall_phase }
-  }
+  let(:install_phase) { -> { app.install_phase } }
+  let(:uninstall_phase) { -> { app.uninstall_phase } }
 
   before do
     TestHelper.install_without_artifacts(cask)

Library/Homebrew/cask/test/cask/artifact/generic_artifact_test.rb

@@ -4,7 +4,7 @@ describe Hbc::Artifact::Artifact do
   let(:cask) { Hbc.load("with-generic-artifact") }
 
   let(:install_phase) {
-    lambda { Hbc::Artifact::Artifact.new(cask).install_phase }
+    -> { Hbc::Artifact::Artifact.new(cask).install_phase }
   }
 
   let(:source_path) { cask.staged_path.join("Caffeine.app") }

Library/Homebrew/cask/test/cask/artifact/suite_test.rb

@@ -3,9 +3,7 @@ require "test_helper"
 describe Hbc::Artifact::Suite do
   let(:cask) { Hbc.load("with-suite") }
 
-  let(:install_phase) {
-    lambda { Hbc::Artifact::Suite.new(cask).install_phase }
-  }
+  let(:install_phase) { -> { Hbc::Artifact::Suite.new(cask).install_phase } }
 
   let(:target_path) { Hbc.appdir.join("Caffeine") }
   let(:source_path) { cask.staged_path.join("Caffeine") }

Library/Homebrew/cask/test/cask/artifact/two_apps_correct_test.rb

@@ -5,7 +5,7 @@ describe Hbc::Artifact::App do
     let(:cask) { Hbc.load("with-two-apps-correct") }
 
     let(:install_phase) {
-      lambda { Hbc::Artifact::App.new(cask).install_phase }
+      -> { Hbc::Artifact::App.new(cask).install_phase }
     }
 
     let(:source_path_mini) { cask.staged_path.join("Caffeine Mini.app") }