Restore puremagic version range limit

Fixup for ac9b97b

Author: kislyuk

requirements.txt

@@ -26,9 +26,9 @@ Jinja2 >= 2.10, < 3
 jsonpointer >= 1.10, < 2
 jsonschema >= 2.6, < 3
 
-# Pinned due to an incompatibility with later versions of puremagic.
+# Version range restricted due to an incompatibility with later versions of puremagic.
 # See https://github.com/HumanCellAtlas/dcp-cli/pull/245.
-puremagic==1.5
+puremagic >= 1.4, < 1.5
 
 PyJWT >= 1.6.4, < 2
 requests >= 2.20.0, < 3