Fix CI on latest ubuntu

The qemu package is no longer available. Fortunately, it's not really
used by the CI script. It uses qemu-system-arm, which is also installed.

Author: jannic

.github/workflows/on-target.yml

@@ -23,7 +23,7 @@ jobs:
           RUSTFLAGS: -C link-arg=-Tlink.x -D warnings
         run: cargo build -p testsuite --target thumbv7m-none-eabi
       - name: Install QEMU
-        run: sudo apt-get update && sudo apt-get install qemu qemu-system-arm
+        run: sudo apt-get update && sudo apt-get install qemu-system-arm
       - name: Run testsuite
         run: |
           qemu-system-arm \