doc: drop mentions to .pow files ($deity REST their soul)

Co-authored-by: Roberto Abdelkader Martínez Pérez <robertomartinezp@gmail.com>

docs/source/examples/shell_tricks.rst

@@ -10,7 +10,8 @@ from query params:
 .. code-block:: console
    :linenos:
 
-   $ cat parallel.pow
+   $ cat parallel-route
+   #!/usr/bin/env sh
    kapow route add '/parallel/{ip1}/{ip2}' - <<-'EOF'
    	ping -c 1 -- "$(kapow get /request/matches/ip1)" | kapow set /response/body &
    	ping -c 1 -- "$(kapow get /request/matches/ip2)" | kapow set /response/body &
@@ -30,5 +31,6 @@ Script debugging
 Bash provides the ``set -x`` builtin command that "After expanding each simple command,
 for command, case command, select command, or arithmetic for command, display the
 expanded value of PS4, followed by the command and its expanded arguments or associated
-word list". This feature can be used to help debugging the `.pow` scripts and, together
-the ``--debug`` option in the server sub-command, the scripts executed in user requests.
+word list".  This feature can be used to help debugging the init programs and,
+together the ``--debug`` option in the server sub-command, the scripts executed
+in user requests.