Fixed typo

Author: ryan-blunden

dockerfile-lint-extension/extension/README.md

@@ -2,7 +2,7 @@
 
 A [Sourcegraph extension](https://docs.sourcegraph.com/extensions/) to lint Dockerfiles on [Sourcegraph.com](https://sourcegraph.com) and GitHub using [Hadolint](https://github.com/hadolint/hadolint).
 
-![dockerfile lint github sourcegraph](https://user-images.githubusercontent.com/133014/49892179-2db21980-fdfd-11e8-9076-ef9f4bfae01a.gif))
+![dockerfile lint github sourcegraph](https://user-images.githubusercontent.com/133014/49892179-2db21980-fdfd-11e8-9076-ef9f4bfae01a.gif)
 
 ## Try it on GitHub