Update dependencies

vendor/tailscale.com/syncs/locked.go

@@ -0,0 +1,32 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package syncs
+
+import (
+	"sync"
+)
+
+// AssertLocked panics if m is not locked.
+func AssertLocked(m *sync.Mutex) {
+	if m.TryLock() {
+		m.Unlock()
+		panic("mutex is not locked")
+	}
+}
+
+// AssertRLocked panics if rw is not locked for reading or writing.
+func AssertRLocked(rw *sync.RWMutex) {
+	if rw.TryLock() {
+		rw.Unlock()
+		panic("mutex is not locked")
+	}
+}
+
+// AssertWLocked panics if rw is not locked for writing.
+func AssertWLocked(rw *sync.RWMutex) {
+	if rw.TryRLock() {
+		rw.RUnlock()
+		panic("mutex is not rlocked")
+	}
+}