docs: replace ' with " in windows tarfile examples

The examples for using python to unpack a tarfile on windows used '
not ". I thought they were interchangable, but they are not. Only "
works like I expect.

Author: rouilj

doc/installation.txt

@@ -76,7 +76,7 @@ program you can run ``python demo.py`` instead.)
 1. ``python3 -m pip download roundup``
 2. ``tar -xzvf roundup-2.2.0.tar.gz``
 
-   * if you don't have a tar command, ``python3 -c 'import tarfile, sys; tarfile.open(sys.argv[1]).extractall();' roundup-2.2.0.tar.gz`` can be used.
+   * if you don't have a tar command, ``python3 -c "import tarfile, sys; tarfile.open(sys.argv[1]).extractall();" roundup-2.2.0.tar.gz`` can be used.
 
 3. ``cd roundup-2.2.0``
 4. ``python3 demo.py``

website/www/index.txt

@@ -184,7 +184,7 @@ Follow the source gratification mode with these steps (change the
 2. ``tar -xzvf roundup-2.3.0.tar.gz``
 
    * if you don't have a tar command (e.g windows), use:
-     ``python -c 'import tarfile, sys; tarfile.open(sys.argv[1]).extractall();' roundup-2.3.0.tar.gz``
+     ``python -c "import tarfile, sys; tarfile.open(sys.argv[1]).extractall();" roundup-2.3.0.tar.gz``
 
 
 3. ``cd roundup-2.3.0``