ci: allow manual dispatch of superchain build (#4696)

Need this for testing.
Also fixed a deprecated input parameter name in the workflow.

---

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[Apache 2.0 license]: https://www.apache.org/licenses/LICENSE-2.0

.github/workflows/docker-images.yml

@@ -2,6 +2,7 @@
 name: Docker Images
 
 on:
+  workflow_dispatch: {}
   merge_group: {}
   pull_request:
     branches: [main, release]
@@ -126,7 +127,7 @@ jobs:
         with:
           # Disable parallelism because IO contention makes it too slow on GitHub
           # workers...
-          config-inline: |-
+          buildkitd-config-inline: |-
             [worker.oci]
               max-parallelism = 1