log: make Default doc comment consistent with package doc
None of the other, older, doc comments use the '*Logger' form, and while
'Logger' and 'logger' are both used in the package doc comment, the
common term used with the intended meaning is 'standard logger', which
appears another eleven times in doc comments.
Change-Id: I089103198fc82390517615eb27bbe7ef77107d34
Reviewed-on: https://go-review.googlesource.com/c/go/+/273486 Reviewed-by: Rob Pike <r@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
Trust: Ian Lance Taylor <iant@golang.org>