cask: remove os_versions

This was originally used by the API but was replaced months
ago by SimulateSystem. Essentially, it's only current use
was in the #to_h method but is not used internally at all
when creating cask instances from the API JSON.

Library/Homebrew/cask/cask.rb

@@ -114,24 +114,6 @@ module Cask
                           .reverse
     end
 
-    def os_versions
-      # TODO: use #to_hash_with_variations instead once all casks use on_system blocks
-      @os_versions ||= begin
-        version_os_hash = {}
-        actual_version = MacOS.full_version.to_s
-
-        MacOSVersions::SYMBOLS.each do |os_name, os_version|
-          MacOS.full_version = os_version
-          cask = CaskLoader.load(full_name)
-          version_os_hash[os_name] = cask.version if cask.version != version
-        end
-
-        version_os_hash
-      ensure
-        MacOS.full_version = actual_version if actual_version
-      end
-    end
-
     def full_name
       return token if tap.nil?
       return token if tap.user == "Homebrew"
@@ -307,7 +289,6 @@ module Cask
         "url_specs"            => url_specs,
         "appcast"              => appcast,
         "version"              => version,
-        "versions"             => os_versions,
         "installed"            => versions.last,
         "outdated"             => outdated?,
         "sha256"               => sha256,

Library/Homebrew/test/support/fixtures/cask/caffeine.json

@@ -10,8 +10,6 @@
   "url": "https://www.example.com/cask/caffeine.zip",
   "appcast": null,
   "version": "1.2.3",
-  "versions": {
-  },
   "installed": null,
   "outdated": false,
   "sha256": "67cdb8a02803ef37fdbf7e0be205863172e41a561ca446cd84f0d7ab35a99d94",

Library/Homebrew/test/support/fixtures/cask/everything.json

@@ -16,8 +16,6 @@
   },
   "appcast": null,
   "version": "1.2.3",
-  "versions": {
-  },
   "installed": null,
   "outdated": false,
   "sha256": "c64c05bdc0be845505d6e55e69e696a7f50d40846e76155f0c85d5ff5e7bbb84",