auth: Remove "shared" aka "global" secrets.

server/auth/authdb/erroring.go

Index: server/auth/authdb/erroring.go
diff --git a/server/auth/authdb/erroring.go b/server/auth/authdb/erroring.go
index 92e0c4ae9afac073e1e3806e1a0fc6ac1047e2ff..6738ef625aa2b9231a27e34dd293158197ceb115 100644
--- a/server/auth/authdb/erroring.go
+++ b/server/auth/authdb/erroring.go
@@ -12,7 +12,6 @@ import (
 	"github.com/luci/luci-go/common/logging"
 	"github.com/luci/luci-go/server/auth/identity"
 	"github.com/luci/luci-go/server/auth/signing"
-	"github.com/luci/luci-go/server/secrets"
 )
 
 // ErroringDB implements DB by forbidding all access and returning errors.
@@ -36,15 +35,6 @@ func (db ErroringDB) IsMember(c context.Context, id identity.Identity, groups ..
 	return false, db.Error
 }
 
-// SharedSecrets is secrets.Store with secrets in Auth DB.
-//
-// Such secrets are usually generated on central Auth Service and are known
-// to all trusted services (so that they can use them to exchange data).
-func (db ErroringDB) SharedSecrets(c context.Context) (secrets.Store, error) {
-	logging.Errorf(c, "%s", db.Error)
-	return nil, db.Error
-}
-
 // GetCertificates returns a bundle with certificates of a trusted signer.
 func (db ErroringDB) GetCertificates(c context.Context, id identity.Identity) (*signing.PublicCertificates, error) {
 	logging.Errorf(c, "%s", db.Error)