Format the lint-once resolver changes

Reflow the heredoc RUN fixture array in the BuildKit heredoc test to
satisfy prettier --check, which rejected the single-line form. No
behavioural change to the tests or the resolver.

test/packaging/lint-once.test.ts

@@ -646,9 +646,13 @@ describe("the resolver reads what the shell would run", () => {
     it("reads the body of a BuildKit heredoc RUN step", () => {
         expect(
             dockerRunCommands(
-                ["FROM scratch", "RUN <<EOF", "yarn run prettier --check .", "EOF", "RUN echo done"].join(
+                [
-                    "\n",
+                    "FROM scratch",
-                ),
+                    "RUN <<EOF",
+                    "yarn run prettier --check .",
+                    "EOF",
+                    "RUN echo done",
+                ].join("\n"),
             ),
         ).toContain("yarn run prettier --check .");
     });