s390/docs: Remove section about script debugging from Debugging390.txt

The section about debugging scripting languages has nothing to do with
s390 (and the example is even apparently taken from a i586 host instead),
so let's remove this chapter from the file.

Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>