fix(ci): add jit to luarc globals for lua-language-server

jit is a standard LuaJIT global (like vim), needed by lib.lua for
platform detection via jit.os and jit.arch.

.luarc.json

@@ -1,7 +1,7 @@
 {
   "runtime.version": "Lua 5.1",
   "runtime.path": ["lua/?.lua", "lua/?/init.lua"],
-  "diagnostics.globals": ["vim"],
+  "diagnostics.globals": ["vim", "jit"],
   "workspace.library": ["$VIMRUNTIME/lua", "${3rd}/luv/library"],
   "workspace.checkThirdParty": false,
   "completion.callSnippet": "Replace"