docs: Use reqpart in example.ks

The partitioning defined in the example kickstart file suggests that the
installer supports hybrid boot. That's misleading and not true. Let's use
the `reqpart` kickstart command to automatically create partitions required
by the detected platform instead of creating all of them for all platforms.

Note: The `reqpart` command doesn't work with `bootloader --location=none` or
`bootloader --disabled`, so this commit depends on the installer's support
for bootupd: https://github.com/rhinstaller/anaconda/pull/5298/

docs/example.ks

@@ -2,11 +2,9 @@ text
 
 # Basic partitioning
 clearpart --all --initlabel --disklabel=gpt
-part prepboot  --size=4    --fstype=prepboot
+part /boot --size=1000  --fstype=ext4 --label=boot
-part biosboot  --size=1    --fstype=biosboot
-part /boot/efi --size=100  --fstype=efi
-part /boot     --size=1000  --fstype=ext4 --label=boot
 part / --grow --fstype xfs
+reqpart
 
 ostreecontainer --url quay.io/centos-bootc/fedora-bootc:eln	--no-signature-verification
 # Or: quay.io/centos-bootc/centos-bootc-dev:stream9