strings: correct NewReader documentation
The provided description for `NewReader` says that the underlying string is read-only. but the following example shows that this is not the case.
<br />
rd := strings.NewReader("this is a text")
rd.Reset("new text") <--- underlying string gets updated here
Change-Id: I95c7099c2e63670c84307d4317b702bf13a4025a
GitHub-Last-Rev:
a16a60b0f1e25d19e05e664c5b41ca57c4fcd9b2
GitHub-Pull-Request: golang/go#60074
Reviewed-on: https://go-review.googlesource.com/c/go/+/493817
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>