module: remove trailing '@' for versionless Versions

Change-Id: I836874b96805779bfb1ddf3cd20abe806378fbb3
Reviewed-on: https://go-review.googlesource.com/c/mod/+/205857
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>
1 file changed