0.15.2 standard library docs don't include changes made in 0.15.2

[squeek502]

For example, takeDelimiterExclusive has the 0.15.1 doc comment and source code:

https://ziglang.org/documentation/0.15.2/std/#std.Io.Reader.takeDelimiterExclusive

https://github.com/ziglang/zig/blob/3db960767d12b6214bcf43f1966a037c7a586a12/lib/std/Io/Reader.zig#L786-L815

instead of the 0.15.2:

https://github.com/ziglang/zig/blob/e4cbd752c8c05f131051f8c873cff7823177d7d3/lib/std/Io/Reader.zig#L796-L819