Typo

Author: nthiery

Dockerfile

@@ -2,7 +2,7 @@
 # Reference: https://mybinder.readthedocs.io/en/latest/dockerfile.html#preparing-your-dockerfile
 
 # Temporary work around: the first 8.2 image that was pushed to dockerhub was incompatible
-FROM sagemath/sagemath@sha256:e933509b105f36b9b7de892af847ade7753e058c5d9e0c0f280f591b85ad996d`
+FROM sagemath/sagemath@sha256:e933509b105f36b9b7de892af847ade7753e058c5d9e0c0f280f591b85ad996d
 # FROM sagemath/sagemath:8.2
 
 # Copy the contents of the repo in ${HOME}