docs: fix directory separator for Windows

Author: kenjis

user_guide_src/source/installation/running.rst

@@ -146,7 +146,7 @@ Adding Host Alias
 -----------------
 
 Add a host alias in your "hosts" file, typically **/etc/hosts** on unix-type platforms,
-or **c:/Windows/System32/drivers/etc/hosts** on Windows.
+or **c:\Windows\System32\drivers\etc\hosts** on Windows.
 
 Add a line to the file.
 This could be ``myproject.local`` or ``myproject.test``, for instance::