Update setup.py

Author: Kazuki Suzuki Przyborowski

setup.py

@@ -131,7 +131,7 @@
     name = "{}"
     version = "{}"
     readme = "README.md"
-    license = { text = "BSD-3-Clause" }
+    license = {{ text = "BSD-3-Clause" }}
     keywords = []
     description = "{}"
     authors = [