Correct 2 small spelling mistakes on line 274 of aruco.hpp (no code changes)

[JoostScheffer]

Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

• [x] I agree to contribute to the project under Apache 2 License.
• [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
• [x] The PR is proposed to the proper branch
• [x] There is a reference to the original bug report and related work
• [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable Patch to opencv_extra has the same branch name.
• [x] The feature is well documented and sample code can be built with the project CMake

[alalek]

Thank you for contribution!

This patch should go into 3.4 branch first. We will merge changes from 3.4 into 4.x regularly (weekly/bi-weekly).

Please:

• change "base" branch of this PR: 4.x => 3.4 (use "Edit" button near PR title)
• rebase your commits from 4.x onto 3.4 branch. For example: git rebase -i --onto upstream/3.4 upstream/4.x (check list of your commits, save and quit (Esc + "wq" + Enter) where upstream is configured by following this GitHub guide and fetched (git fetch upstream).
• push rebased commits into source branch of your fork (with --force option)

Note: no needs to re-open PR, apply changes "inplace".