cmd/vendor: undo stray edits from CL 384262

cmd/internal/moddeps is currently failing on the longtest builders
because vendored third-party dependencies were accidentally edited as
part of CL 384262 (a global cleanup of the standard library).

Updates #51082

Change-Id: I6f79c8f1177420a51128ce42d6c14fa5dcc4bd7b
Reviewed-on: https://go-review.googlesource.com/c/go/+/398455
Trust: Bryan Mills <[email protected]>
Run-TryBot: Bryan Mills <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>

Author: Bryan C. Mills