Use present indicative tense in std::io::pipe() API docs
The inline documentation for all other free functions in the `std::io` module use the phrase "creates a" instead of "create a", except for the currently nightly-only `std::io::pipe()` function. This commit updates the text to align with the predominant wording in the `std::io` module.
I recognize this PR is quite a minuscule nitpick, so feel free to ignore and close if you disagree and/or there are bigger fish to fry. Thanks in advance! 😄
Relates to https://github.com/rust-lang/rust/issues/127154.
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