Fixed pytest error by removing reference to coverage.

Index: setup.cfg
--- setup.cfg.orig
+++ setup.cfg
@@ -4,9 +4,6 @@ universal = 1
 [aliases]
 test = pytest
 
-[tool:pytest]
-addopts = --cov=blurhash
-
 [egg_info]
 tag_build = 
 tag_date = 0