doc/go1.15: include behavior updates to the context package
doc/go1.15: include behavior updates to the context package

Fixes #40737

Change-Id: I8e2c1e1653d427af1ded6d61df1aa450e3c4d35c
Reviewed-on: https://go-review.googlesource.com/c/go/+/248329
Run-TryBot: Andrew Bonventre <682ad9f487f614f19e8b7cc5d340bdc8e1c1b128@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

CAFxX/go,cloudflare/go,nawawi/go,nawawi/go,CAFxX/go,CAFxX/go,CAFxX/go,golang/go,cloudflare/go,cloudflare/go,golang/go,cloudflare/go,cloudflare/go,CAFxX/go,nawawi/go,golang/go,golang/go,nawawi/go,golang/go,golang/go,golang/go,CAFxX/go,cloudflare/go,nawawi/go,cloudflare/go,nawawi/go,nawawi/go,CAFxX/go,nawawi/go,cloudflare/go,golang/go,CAFxX/go