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

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

examples/basic/03_DynamicLogGrep/DynamicLogGrep

@@ -0,0 +1,5 @@
+#!/bin/sh
+
+kapow route add /apache-logs - <<-'EOF'
+	cat /var/log/apache2/access.log | grep -- "$(kapow get /request/params/pattern)" | kapow set /response/body
+EOF