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. :smile:

0 files changed, 0 insertions, 0 deletions