Update CHANGELOG.md

CHANGELOG.md

@@ -2,7 +2,7 @@
 
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-## [5.3.1 - Prefetching Threadh](https://github.com/onevcat/Kingfisher/releases/tag/5.3.1) (2019-03-28)
+## [5.3.1 - Prefetching Thread](https://github.com/onevcat/Kingfisher/releases/tag/5.3.1) (2019-03-28)
 
 #### Fix
 * Some thread issues which may cause crash when loading images by `ImagePrefetcher`. [#1150](https://github.com/onevcat/Kingfisher/pull/1150)