Update dependencies and vendor (#1761)

vendor/github.com/slack-go/slack/webhooks_go113.go

@@ -1,3 +1,4 @@
+//go:build go1.13
 // +build go1.13
 
 package slack
@@ -6,26 +7,25 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
+	"fmt"
 	"net/http"
-
-	"github.com/pkg/errors"
 )
 
 func PostWebhookCustomHTTPContext(ctx context.Context, url string, httpClient *http.Client, msg *WebhookMessage) error {
 	raw, err := json.Marshal(msg)
 	if err != nil {
-		return errors.Wrap(err, "marshal failed")
+		return fmt.Errorf("marshal failed: %w", err)
 	}
 
 	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(raw))
 	if err != nil {
-		return errors.Wrap(err, "failed new request")
+		return fmt.Errorf("failed new request: %w", err)
 	}
 	req.Header.Set("Content-Type", "application/json")
 
 	resp, err := httpClient.Do(req)
 	if err != nil {
-		return errors.Wrap(err, "failed to post webhook")
+		return fmt.Errorf("failed to post webhook: %w", err)
 	}
 	defer resp.Body.Close()