core: add postprocess progress when upload success (#2535)

* core: add postprocess progress when upload success

* Update packages/@uppy/core/src/index.js

Co-authored-by: Renée Kooi <renee@kooi.me>

packages/@uppy/core/src/index.js

@@ -1076,6 +1076,9 @@ class Uppy {
       const currentProgress = this.getFile(file.id).progress
       this.setFileState(file.id, {
         progress: Object.assign({}, currentProgress, {
+          postprocess: this.postProcessors.length > 0 ? {
+            mode: 'indeterminate'
+          } : null,
           uploadComplete: true,
           percentage: 100,
           bytesUploaded: currentProgress.bytesTotal