Fix BuildDuration type

Author: zrochler

gitlab/payload.go

@@ -139,7 +139,7 @@ type BuildEventPayload struct {
 	BuildStatus       string      `json:"build_status"`
 	BuildStartedAt    customTime  `json:"build_started_at"`
 	BuildFinishedAt   customTime  `json:"build_finished_at"`
-	BuildDuration     int64       `json:"build_duration"`
+	BuildDuration     float64     `json:"build_duration"`
 	BuildAllowFailure bool        `json:"build_allow_failure"`
 	ProjectID         int64       `json:"project_id"`
 	ProjectName       string      `json:"project_name"`