time: in NewTicker, document that the 1st tick comes after d
time: in NewTicker, document that the 1st tick comes after d

Fixes #42245

Change-Id: I3b298ab6be65569389873d68bd3c6e49cf892c69
Reviewed-on: https://go-review.googlesource.com/c/go/+/265818
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Reviewed-by: Rob Pike <4dc7c9ec434ed06502767136789763ec11d2c4b7@golang.org>
Trust: Alberto Donizetti <90b16103a35511ced020676f3544f17117fb4c92@gmail.com>

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