tool: remove bootspec.json

This fixture is not necessary anymore as we have enough integration
tests.

rust/tool/bootspec.json

@@ -1,23 +0,0 @@
-{
-  "v1": {
-    "init": "/run/current-system/init",
-    "initrd": "/run/current-system/initrd",
-    "kernel": "/run/current-system/kernel",
-    "kernelParams": [
-      "amd_iommu=on",
-      "amd_iommu=pt",
-      "iommu=pt",
-      "kvm.ignore_msrs=1",
-      "kvm.report_ignored_msrs=0",
-      "udev.log_priority=3",
-      "systemd.unified_cgroup_hierarchy=1",
-      "loglevel=4"
-    ],
-    "label": "LanzaOS",
-    "toplevel": "/run/current-system",
-    "specialisation": {},
-    "extensions": {
-      "lanzaboote": { "osRelease": "/etc/os-release" }
-    }
-  }
-}