fix version replacement in setup.py (gitpython-developers#1500)

It would fail to perform the replacement, but unfortunately wouldn't
stop the release process.

The latter could be done, but isn't implemented either as it's hard
to test given everything is runtime.

Author: Byron

setup.py

@@ -47,7 +47,7 @@ def _stamp_version(filename: str) -> None:
         with open(filename, "r") as f:
             for line in f:
                 if "__version__ =" in line:
-                    line = line.replace("'git'", "'%s'" % VERSION)
+                    line = line.replace("\"git\"", "'%s'" % VERSION)
                     found = True
                 out.append(line)
     except OSError: