docs: remove gm library references from README

Author: angelcaamal

functions/imagemagick/README.md

@@ -1,8 +1,8 @@
 <img src="https://avatars2.githubusercontent.com/u/2810941?v=3&s=96" alt="Google Cloud Platform logo" title="Google Cloud Platform" align="right" height="96" width="96"/>
 
-# Google Cloud Functions ImageMagick sample
+# Google Cloud Functions imagemagick sample
 
-This sample shows you how to blur an image using ImageMagick in a
+This sample shows you how to blur an image using sharp in a
 Storage-triggered Cloud Function.
 
 View the [source code][code].