Doc: cmdline.rst: Include -P and -R in usage (#122590)

* ``-P``: safe path (https://docs.python.org/3/using/cmdline.html#cmdoption-P)
* ``-R``: hash randomization (https://docs.python.org/3/using/cmdline.html#cmdoption-R)

Author: wimglenn

Doc/using/cmdline.rst

@@ -24,7 +24,7 @@ Command line
 
 When invoking Python, you may specify any of these options::
 
-    python [-bBdEhiIOqsSuvVWx?] [-c command | -m module-name | script | - ] [args]
+    python [-bBdEhiIOPqRsSuvVWx?] [-c command | -m module-name | script | - ] [args]
 
 The most common use case is, of course, a simple invocation of a script::