[release-branch.go1.25] 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.

For #76961
Fixes #76973

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>
(cherry picked from commit 1b3db48db7afc3fe17440af28cdeac67a0d048f1)
Reviewed-on: https://go-review.googlesource.com/c/go/+/734520
Reviewed-by: Junyang Shao <shaojunyang@google.com>

1 files changed, 0 insertions, 12 deletions

diff --git a/src/errors/join.go b/src/errors/join.go
index dd50089c29..349fc06ed9 100644
--- a/src/errors/join.go
+++ b/src/errors/join.go
@@ -26,18 +26,6 @@ func Join(errs ...error) error {
 	if n == 0 {
 		return nil
 	}
-	if n == 1 {
-		for _, err := range errs {
-			if err != nil {
-				if _, ok := err.(interface {
-					Unwrap() []error
-				}); ok {
-					return err
-				}
-			}
-		}
-	}
-
 	e := &joinError{
 		errs: make([]error, 0, n),
 	}