playbooks/remove-autorestic: quote the ! in the binary-absent verify (YAML tag indicator)

YAML treats a leading `!` as a tag indicator, so the unquoted
`shell: ! command -v autorestic >/dev/null` was parsed as a tagged
scalar with the `!` stripped. The verify ended up running just
`command -v autorestic >/dev/null` — which exits non-zero when
autorestic is absent, the OPPOSITE of what the assertion needed.

Quoted version `"! command -v autorestic >/dev/null"` survives
parsing and gives the intended bash negation.

playbooks/remove-autorestic.yaml

@@ -80,7 +80,11 @@ verify:
     changed_when: "false"
 
   - name: No autorestic binary on PATH
-    shell: ! command -v autorestic >/dev/null
+    # Quoted because YAML treats a leading `!` as a tag indicator —
+    # unquoted, the parser strips it and the verify ends up running
+    # `command -v autorestic` (exits non-zero when autorestic is gone,
+    # which is the OPPOSITE of what we want here).
+    shell: "! command -v autorestic >/dev/null"
     changed_when: "false"
 
   - name: systemd no longer knows about autorestic units