tests: drop workaround for older busted versions

No necessary anymore, now that we ship our own up-to-date version.

spec/unit/commonrequire.lua

@@ -1,39 +1,3 @@
--- Check if we're running a busted version recent enough that we don't need to deal with the LuaJIT hacks...
--- That currently means > 2.0.0 (i.e., scm-2, which isn't on LuaRocks...).
-local busted_ok = false
-for name, _ in pairs(package.loaded) do
-    if name == "busted.luajit" then
-        busted_ok = true
-        break
-    end
-end
-
--- Don't try to overwrite metatables so we can use --auto-insulate-tests
--- Shamelessly copied from https://github.com/Olivine-Labs/busted/commit/2dfff99bda01fd3da56fd23415aba5a2a4cc0ffd
-if not busted_ok then
-    local ffi = require "ffi"
-
-    local original_metatype = ffi.metatype
-    local original_store = {}
-    ffi.metatype = function (primary, ...)
-        if original_store[primary] then
-            return original_store[primary]
-        end
-        local success, result, err = pcall(original_metatype, primary, ...)
-        if not success then
-            -- hard error was thrown
-            error(result, 2)
-        end
-        if not result then
-            -- soft error was returned
-            return result, err
-        end
-        -- it worked, store and return
-        original_store[primary] = result
-        return result
-    end
-end
-
 package.path = "?.lua;common/?.lua;frontend/?.lua;" .. package.path
 package.cpath = "?.so;common/?.so;/usr/lib/lua/?.so;" .. package.cpath