Skip integration specs unless periphery is installed

[github-actions[bot]]

Danger has errored

[!] Invalid Dangerfile file: error: ["bin/periphery", "scan", "--project", "spec/support/fixtures/test.xcodeproj", "--schemes", "test", "--targets", "test", "--disable-update-check", "--quiet", "--format", "checkstyle"] exited with status code 1. error: This version of Periphery only supports Swift >= 5.9, you`re using swift-driver version: 1.75.2 Apple Swift version 5.8.1 (swiftlang-5.8.0.124.5 clang-1403.0.22.11.100) Target: x86_64-apple-macosx13.0.

 #  from Dangerfile:8
 #  -------------------------------------------
 #  periphery.binary_path = 'bin/periphery'
 >  periphery.scan(project: 'spec/support/fixtures/test.xcodeproj', schemes: 'test', targets: 'test') do |violation|
 #    !violation.message.include?('unused')
 #  -------------------------------------------

Generated by :no_entry_sign: Danger