Modify hello to demonstrate apt:// without ${PV}

With the introduction of do_apt_unpack, we can set custom ${S}.

With that feature in place it is no longer mandatory to specify
the ${PV} of the package.

${PV} was mandatory before because do_apt_fetch was unpacking
the contents into a folder named "<debian_source>-<debian-source-version>"
hardcoding ${S} to it. So we needed to know the correct
${PV}(debian-source-version) beforehand.

Signed-off-by: Vijai Kumar K <Vijaikumar_Kanagarajan@mentor.com>

meta-isar/recipes-app/hello/hello_2.10.bb

@@ -1,11 +0,0 @@
-# Example recipe to rebuild a debian source package
-#
-# This software is a part of ISAR.
-# Copyright (c) Siemens AG, 2019
-#
-# SPDX-License-Identifier: MIT
-
-require hello.inc
-
-DEFAULT_PREFERENCE_debian-buster = "1"
-DEFAULT_PREFERENCE_debian-stretch = "1"

meta-isar/recipes-app/hello/hello_2.9.bb

@@ -1,8 +0,0 @@
-# Example recipe to rebuild a debian source package
-#
-# This software is a part of ISAR.
-# Copyright (c) Siemens AG, 2019
-#
-# SPDX-License-Identifier: MIT
-
-require hello.inc