present: remove extraneous line
present: remove extraneous line

There was an extra line in the documentation for the
present package that appears to be a copy paste from the
previous paragraph. This removes that line.

Fixes #21891

Change-Id: Ic50840b2210e3d93ac452a659e29b6feaa33c7b7
Reviewed-on: https://go-review.googlesource.com/63811
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools