formula_test: Fix test_requirements for Linuxbrew
formula_test: Fix test_requirements for Linuxbrew

Fix the test failure:
FormulaTests#test_requirements [Library/Homebrew/test/formula_test.rb:689]:
- #<X11Requirement: "x11" [:recommended] min_version=0.0.0>}>
+ #<XorgRequirement: "x11" [:recommended]>}>

rwhogg/brew,hanxue/linuxbrew,maxim-belkin/brew,rwhogg/brew,Linuxbrew/brew,Linuxbrew/brew,rwhogg/brew,Linuxbrew/brew,hanxue/linuxbrew,maxim-belkin/brew,maxim-belkin/brew,hanxue/linuxbrew,Linuxbrew/brew