CI: Use newer version of autopkgtest

To avoid errors such as this:
```
Running setup script /usr/share/autopkgtest/setup-commands/setup-testbed...
awk: fatal: cannot open file `/etc/apt/sources.list' for reading: No such file or directory
sh: Attempting to set up Debian/Ubuntu apt sources automatically
Failed to auto-detect apt mirror; set $MIRROR explicitly
```

.github/workflows/network-manager.yml

@@ -35,6 +35,8 @@ jobs:
         run: |
           sudo apt update
           sudo apt install autopkgtest ubuntu-dev-tools devscripts openvswitch-switch linux-modules-extra-$(uname -r)
+          pull-lp-debs autopkgtest noble
+          sudo dpkg -i autopkgtest_*_all.deb
       - name: Prepare test
         run: |
           pull-lp-source netplan.io
@@ -60,7 +62,7 @@ jobs:
       # work around LP: #1878225 as fallback
       - name: Preparing autopkgtest-build-lxd
         run: |
-          sudo patch /usr/bin/autopkgtest-build-lxd .github/workflows/snapd.patch
+          sudo patch /usr/bin/autopkgtest-build-lxd .github/workflows/snapd.noble.patch
           autopkgtest-build-lxd ubuntu-daily:noble
       - name: Run autopkgtest
         run: |

.github/workflows/snapd.noble.patch

@@ -0,0 +1,9 @@
+@@ -70,6 +70,8 @@
+
+     sleep 5
+     if "$COMMAND" exec "$CONTAINER" -- systemctl mask serial-getty@getty.service; then
++       "$COMMAND" exec "$CONTAINER" -- systemctl mask snapd.service
++       "$COMMAND" exec "$CONTAINER" -- systemctl mask snapd.seeded.service
+        "$COMMAND" exec "$CONTAINER" -- reboot
+     fi
+