ci: Point bootc revdep at OpenConfig-compatible branch

The open_config() return type changed from a tuple to the OpenConfig
struct. Point the bootc reverse-dep CI at bootc-dev/bootc#2044 which
has the matching API update, until that PR is merged to main.

Assisted-by: OpenCode (Claude Opus 4)
Signed-off-by: Colin Walters <walters@verbum.org>

Author: cgwalters

.github/workflows/bootc-revdep.yml

@@ -44,3 +44,8 @@ jobs:
 
       - name: Build and test bootc with local composefs-rs
         run: just bootc/test
+        env:
+          # Use bootc branch with OpenConfig API compatibility
+          # TODO: revert to main once bootc-dev/bootc#2044 is merged
+          COMPOSEFS_BOOTC_REPO: https://github.com/cgwalters/bootc
+          COMPOSEFS_BOOTC_REF: prep-composefs-manifest