Bump stackhpc.linux collection to v1.2.3

Closes-Bug: #2073100
Change-Id: Ied06ee3380a149c4c8d082562c93f9b771457cb4

releasenotes/notes/fix-systemd-networkd-enabling-10bf4e5f0903c311.yaml

+---
+fixes:
+  - |
+    Fixes a bug where systemd-networkd was not permanently enabled when the
+    unit was already in state ``runtime-enabled``.
+    `LP#2073100 <https://launchpad.net/bugs/2073100>`__

requirements.yml

@@ -8,7 +8,7 @@ collections:
   - name: openstack.cloud
     version: '<3'
   - name: stackhpc.linux
-    version: 1.2.1
+    version: 1.2.3
   - name: stackhpc.network
     version: 1.0.0
   - name: stackhpc.openstack