chore: normalize CompatHelper subdirs block-scalar style

`|2-` and `|-` parse identically here (auto-detection picks up the
2-space indent from the first non-empty content line), but `|-` is
the conventional form used elsewhere in the repo.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: mtfishman

.github/workflows/CompatHelper.yml

@@ -12,7 +12,7 @@ jobs:
     uses: "ITensor/ITensorActions/.github/workflows/CompatHelper.yml@mf/subdir-inputs"
     with:
       localregistry: "https://github.com/ITensor/ITensorRegistry.git"
-      subdirs: |2-
+      subdirs: |-
 
         docs
         examples