.github/workflows: adjust to bootc changes

The rule in the Justfile got renamed.

Signed-off-by: Allison Karlitskaya <[email protected]>

Author: allisonkarlitskaya

.github/workflows/bootc-revdep.yml

@@ -99,7 +99,7 @@ jobs:
 
       - name: Build sealed bootc image
         working-directory: bootc
-        run: just build-sealed
+        run: just variant=composefs-sealeduki-sdboot build
 
       - name: Run composefs tests
         working-directory: bootc