Fix typo in subprocess

Author: Martin D. Weinberg

conf.py

@@ -31,9 +31,9 @@
 subprocess.run(["git", "checkout", branch])
 subprocess.run(["cp", "CMakeLists.txt", "CMakeLists.txt.orig"])
 fwrite = open("CMakeLists.txt", "w")
-subprocess.Popen(["sed", "-e", "s/VERSION 3.25/VERSION 3.22/", "CMakeLists.txt.orig"], stdout=fwrite)
+pipe = subprocess.Popen(["sed", "-e", "s/VERSION 3.25/VERSION 3.22/", "CMakeLists.txt.orig"], stdout=fwrite)
+pipe.stdout.close()
 fwrite.close()
-subprocess.stdout.close()
 os.chdir(doxy_dir)
 os.system("git submodule update --init --recursive")