Drop LuaJIT 2.0.5 support

Primary CI target is luajit-openresty. Even 2.1.0-beta3 is ancient.

.github/workflows/busted.yml

@@ -7,7 +7,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        lua_version: ["luajit-2.1.0-beta3", "luajit-2.0.5", "luajit-openresty"]
+        lua_version: ["luajit-openresty", "luajit-2.1.0-beta3"]
 
     runs-on: ubuntu-latest
 

kiwi.lua

@@ -871,8 +871,7 @@ do
    function kiwi.error_mask(kinds, invert)
       local mask = 0
       for _, k in ipairs(kinds) do
-         -- must use tonumber only for LuaJIT 2.0 compatibility
-         mask = bor(mask, lshift(1, tonumber(kiwi.ErrKind(k)) --[[@as integer]]))
+         mask = bor(mask, lshift(1, kiwi.ErrKind(k)))
       end
       return invert and bit.bnot(mask) or mask
    end
@@ -941,9 +940,8 @@ do
          end
          local errdata = new_error(kind, message, solver, item)
          local error_mask = solver and solver.error_mask_ or 0
-         -- tonumber only required for LuaJIT 2.0 compatibility
          return item,
-            band(error_mask, lshift(1, tonumber(kind) --[[@as integer]])) == 0 and error(errdata)
+            band(error_mask, lshift(1, kind --[[@as integer]])) == 0 and error(errdata)
                or errdata
       end
       return item