Update vendoring

vendor/github.com/aws/aws-sdk-go/service/dynamodb/dynamodbattribute/encode.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"reflect"
 	"strconv"
+	"time"
 
 	"github.com/aws/aws-sdk-go/service/dynamodb"
 )
@@ -215,6 +216,15 @@ func (e *Encoder) encode(av *dynamodb.AttributeValue, v reflect.Value, fieldTag
 }
 
 func (e *Encoder) encodeStruct(av *dynamodb.AttributeValue, v reflect.Value) error {
+
+	// To maintain backwards compatibility with ConvertTo family of methods which
+	// converted time.Time structs to strings
+	if t, ok := v.Interface().(time.Time); ok {
+		s := t.Format(time.RFC3339Nano)
+		av.S = &s
+		return nil
+	}
+
 	av.M = map[string]*dynamodb.AttributeValue{}
 	fields := unionStructFields(v.Type(), e.MarshalOptions)
 	for _, f := range fields {