Revert "errors: optimize errors.Join for single unwrappable errors"

This reverts CL 635115.

Reason for revert: The new behavior does not match the function documentation.

Fixes #76961

Change-Id: If2450aa4efba28c7a12887a5b306c231a836e740
Reviewed-on: https://go-review.googlesource.com/c/go/+/731981
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

1 files changed, 0 insertions, 10 deletions

diff --git a/src/errors/join.go b/src/errors/join.go
index 08a79867c6..730bf7043c 100644
--- a/src/errors/join.go
+++ b/src/errors/join.go
@@ -27,16 +27,6 @@ func Join(errs ...error) error {
 	if n == 0 {
 		return nil
 	}
-	if n == 1 {
-		for _, err := range errs {
-			if _, ok := err.(interface {
-				Unwrap() []error
-			}); ok {
-				return err
-			}
-		}
-	}
-
 	e := &joinError{
 		errs: make([]error, 0, n),
 	}