[client] Do not log the WireGuard key on a parse failure (#7379)

The error already says what went wrong: an invalid base64 payload
reports the offending byte offset, and a wrong key size reports the
length. Passing the key itself adds nothing an operator can act on, and
the line is emitted at Error level, so it reaches every log sink and
every debug bundle.

client/internal/connect.go

@@ -242,7 +242,7 @@ func (c *ConnectClient) run(mobileDependency MobileDependency, runningChan chan
 	wrapErr := state.Wrap
 	myPrivateKey, err := wgtypes.ParseKey(c.config.PrivateKey)
 	if err != nil {
-		log.Errorf("failed parsing Wireguard key %s: [%s]", c.config.PrivateKey, err.Error())
+		log.Errorf("failed parsing Wireguard key: %s", err)
 		return wrapErr(err)
 	}