cmd/go: clarify vcs suffix to repo mapping

For #71635

Change-Id: I12ec2a810cfcaf2565b0d9c518b0921ec54e9f12
Reviewed-on: https://go-review.googlesource.com/c/go/+/648475
Reviewed-by: Michael Matloob <matloob@golang.org>
Auto-Submit: Sam Thanawalla <samthanawalla@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Sam Thanawalla <samthanawalla@google.com>

src/cmd/go/alldocs.go

@@ -2924,12 +2924,12 @@
 //	import "example.org/user/foo.hg"
 //
 // denotes the root directory of the Mercurial repository at
-// example.org/user/foo or foo.hg, and
+// example.org/user/foo, and
 //
 //	import "example.org/repo.git/foo/bar"
 //
 // denotes the foo/bar directory of the Git repository at
-// example.org/repo or repo.git.
+// example.org/repo.
 //
 // When a version control system supports multiple protocols,
 // each is tried in turn when downloading. For example, a Git

src/cmd/go/internal/help/helpdoc.go

@@ -214,12 +214,12 @@ For example,
 	import "example.org/user/foo.hg"
 
 denotes the root directory of the Mercurial repository at
-example.org/user/foo or foo.hg, and
+example.org/user/foo, and
 
 	import "example.org/repo.git/foo/bar"
 
 denotes the foo/bar directory of the Git repository at
-example.org/repo or repo.git.
+example.org/repo.
 
 When a version control system supports multiple protocols,
 each is tried in turn when downloading. For example, a Git