I will fix readme update for binary search in cpp as it is not ticked.

#### This issue is about [readme](link to resource for the Algo/DS).

- [x] Issue Title is in form `Algo/DS Name [Language]`.
- [x] I searched or browsed the repo’s other issues to ensure this is not a duplicate.
- [x] This Algo/DS is worth adding to this repository.
- [x] Assign this issue to me (I want to work on this).
- [x] I ensure that I am not already assigned to 2 or more issues.
- [x] I will send my PR only after I'm assigned to this issue by any maintainer.
- [x] I understand that I will be unassigned from this issue if I fail to send a PR for this within a week.

Start by locating the repository README and its binary search entry for C++. Check how completed algorithms are represented in the list, then update the unchecked entry and verify the rendered README shows it as completed.

Written by the indexing model from the issue text.