fix(types): correct LuaLS annotations in oauth and gcal

lua/pending/sync/oauth.lua

@@ -29,18 +29,18 @@ local M = {}
 
 ---@param args string[]
 ---@param opts? table
----@return vim.SystemCompleted
+---@return { code: integer, stdout: string, stderr: string }
 function M.system(args, opts)
   local co = coroutine.running()
   if not co then
-    return vim.system(args, opts or {}):wait()
+    return vim.system(args, opts or {}):wait() --[[@as { code: integer, stdout: string, stderr: string }]]
   end
   vim.system(args, opts or {}, function(result)
     vim.schedule(function()
       coroutine.resume(co, result)
     end)
   end)
-  return coroutine.yield()
+  return coroutine.yield() --[[@as { code: integer, stdout: string, stderr: string }]]
 end
 
 ---@param fn fun(): nil