chore(all): review error wrappings

- remove repetitive `cannot` and `failed` prefixes
- rename `unmarshaling` to `decoding`

internal/provider/windscribe/connection_test.go

@@ -38,7 +38,7 @@ func Test_Provider_GetConnection(t *testing.T) {
 		"error": {
 			storageErr: errTest,
 			errWrapped: errTest,
-			errMessage: "cannot filter servers: test error",
+			errMessage: "filtering servers: test error",
 		},
 		"default OpenVPN TCP port": {
 			filteredServers: []models.Server{

internal/provider/windscribe/updater/api.go

@@ -62,7 +62,7 @@ func fetchAPI(ctx context.Context, client *http.Client) (
 
 	decoder := json.NewDecoder(response.Body)
 	if err := decoder.Decode(&data); err != nil {
-		return data, fmt.Errorf("failed unmarshaling response body: %w", err)
+		return data, fmt.Errorf("decoding response body: %w", err)
 	}
 
 	return data, nil