ci: boot loader test VMs keep their own RAM defaults (8 GB to install, 4 GB to test)

.github/workflows/iso-2-gitea-build.yml

@@ -93,7 +93,7 @@ jobs:
       options: --privileged
     strategy:
       fail-fast: false
-      # The runner has ~20 GB of RAM for this: an install VM takes 8 GB, so two at a time (needs the
+      # The runner has ~20 GB of RAM for this: an install VM peaks at 8 GB (4 GB once installed), so two at a time (needs the
       # runner's `capacity: 2`; with 1 they run one after the other).
       max-parallel: 2
       matrix:
@@ -132,7 +132,6 @@ jobs:
         env:
           CI: "1"
           VM_TIMEZONE: UTC
-          VM_MEM: 8G
           # The runner is 4 cores / 8 threads: two VMs with 3 vCPUs leave 2 threads for the host and the runner.
           VM_CPUS: "3"
           VM_ISO_DIR: ${{ github.workspace }}/iso