programs: demo: do not source project_detection.sh directly

Let "demo_common.sh" do all that it's required for these script to
work properly.

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/programs/psa/key_ladder_demo.sh b/programs/psa/key_ladder_demo.sh
index 9559877..e3afb66 100755
--- a/programs/psa/key_ladder_demo.sh
+++ b/programs/psa/key_ladder_demo.sh
@@ -3,7 +3,6 @@
 # Copyright The Mbed TLS Contributors
 # SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
 
-. "${0%/*}/../../framework/scripts/project_detection.sh"
 . "${0%/*}/../../framework/scripts/demo_common.sh"
 
 msg <<'EOF'
diff --git a/programs/psa/psa_hash_demo.sh b/programs/psa/psa_hash_demo.sh
index e10c3db..c2cc87a 100755
--- a/programs/psa/psa_hash_demo.sh
+++ b/programs/psa/psa_hash_demo.sh
@@ -3,7 +3,6 @@
 # Copyright The Mbed TLS Contributors
 # SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
 
-. "${0%/*}/../../framework/scripts/project_detection.sh"
 . "${0%/*}/../../framework/scripts/demo_common.sh"
 
 msg <<'EOF'