[Docs][C++] Fix sentence structure in memory.rst regarding `MemoryManager`

[OmBiradar]

Describe the enhancement requested

https://arrow.apache.org/docs/cpp/memory.html#:~:text=device.-,Each%20device%20has%20a%20default%20memory%20manager%2C%20but%20additional%20instances%20may%20be%20constructed%20(for%20example%2C%20wrapping%20a%20custom%20arrow::MemoryPool%20the%20CPU).%20arrow::MemoryManager%20instances%20which%20specify%20how%20to%20allocate%20memory%20on%20a%20given%20device%20(for%20example%2C%20using%20a%20particular%20arrow::MemoryPool%20on%20the%20CPU).,-Device

There is just some small things missing from these 2 lines which is making it kinda hard to understand exactly. Would be great if it could be fixed by someone who knows what it should have ment.

Component(s)

Documentation

[OmBiradar]

@ianmcook

[OmBiradar]

Sorry for the late reply @thisisnic

I ment to say that

Each device has a default memory manager, but additional instances may be constructed (for example, wrapping a custom arrow::MemoryPool the CPU). arrow::MemoryManager instances which specify how to allocate memory on a given device (for example, using a particular arrow::MemoryPool on the CPU).

this could be

Each device has a default memory manager, but additional instances may be constructed (for example, wrapping a custom arrow::MemoryPool on the CPU). These arrow::MemoryManager instances specify how to allocate memory on a given device (for example, using a particular arrow::MemoryPool on the CPU).

Which I think is a bit more clear.

I could be wrong with the exact meaning.

[OmBiradar]

This was pretty silly, but when I was going through the documentation I was confused.

A single PR for this might be too much. Maybe this could be solved in a collective PR with any other documentation problems combined as a single PR.

[amoeba]

Hi @OmBiradar, creating issue and a PR for a small docs improvement like this one isn't silly and it's even actively encouraged. Small PRs to fix a typo or grammar are easy for maintainers to review. Feel free to submit a PR. See the dev guide if you have any questions about that process.

[OmBiradar]

That's nice!! I guess I will be submitting a few more as I read the docs.

[amoeba]

Issue resolved by pull request 50324
#50324