Update dependencies

vendor/github.com/tailscale/certstore/README.md

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+# certstore
+
+Certstore is a Go library for accessing user identities stored in platform certificate stores. On Windows and macOS, certstore can enumerate user identities and sign messages with their private keys.
+
+## Fork from original module
+
+This is a fork from the [cyolosecurity fork](https://github.com/cyolosecurity/certstore/)
+of the the original [certstore module](https://github.com/github/certstore/). The cyolosecurity
+fork adds some functionality that we require (RSA-PSS support and ability to use the machine
+certificate store instead of the current user certificate store). However, the cyolosecurity
+fork did not update the module name, so we are unable to import it directly, thus leading to
+the Tailscale fork.
+
+As of this writing, the [RSA-PSS PR](https://github.com/github/certstore/pull/18) has been
+under review for several months and the machine certificate store change has not yet been sent
+to the github maintainer for review. Ideally these changes will make their way back into the
+original module and we can
+[discontinue this fork](https://github.com/tailscale/tailscale/issues/2005) at some point in
+the future.
+
+## Example
+
+```go
+package main
+
+import (
+	"crypto"
+	"encoding/hex"
+	"errors"
+	"fmt"
+
+	"crypto/rand"
+	"crypto/sha256"
+
+	"github.com/github/certstore"
+)
+
+func main() {
+	sig, err := signWithMyIdentity("Ben Toews", "hello, world!")
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Println(hex.EncodeToString(sig))
+}
+
+func signWithMyIdentity(cn, msg string) ([]byte, error) {
+	// Open the certificate store for use. This must be Close()'ed once you're
+	// finished with the store and any identities it contains.
+	store, err := certstore.Open()
+	if err != nil {
+		return nil, err
+	}
+	defer store.Close()
+
+	// Get an Identity slice, containing every identity in the store. Each of
+	// these must be Close()'ed when you're done with them.
+	idents, err := store.Identities()
+	if err != nil {
+		return nil, err
+	}
+
+	// Iterate through the identities, looking for the one we want.
+	var me certstore.Identity
+	for _, ident := range idents {
+		defer ident.Close()
+
+		crt, errr := ident.Certificate()
+		if errr != nil {
+			return nil, errr
+		}
+
+		if crt.Subject.CommonName == "Ben Toews" {
+			me = ident
+		}
+	}
+
+	if me == nil {
+		return nil, errors.New("Couldn't find my identity")
+	}
+
+	// Get a crypto.Signer for the identity.
+	signer, err := me.Signer()
+	if err != nil {
+		return nil, err
+	}
+
+	// Digest and sign our message.
+	digest := sha256.Sum256([]byte(msg))
+	signature, err := signer.Sign(rand.Reader, digest[:], crypto.SHA256)
+	if err != nil {
+		return nil, err
+	}
+
+	return signature, nil
+}
+
+```