one more secret key in docs

docs/config.rst

@@ -121,7 +121,8 @@ The following configuration values are used internally by Flask:
     application. It should be a long random string of bytes, although unicode
     is accepted too. For example, copy the output of this to your config::
 
-        python -c 'import os; print(os.urandom(32))'
+        python -c 'import os; print(os.urandom(16))'
+        b'_5#y2L"F4Q8z\n\xec]/'
 
     **Do not reveal the secret key when posting questions or committing code.**