Fix check-base-images (#1080)

In #1070, the `label`
parameter was removed and replaced with a hardcoded value - but the
casing was changed such that the matrix was not being properly
populated.

Author: JackPGreen

.github/workflows/check-base-images.yml

@@ -56,7 +56,7 @@ jobs:
       - name: Check if ${{ matrix.version }} base images updated
         if: steps.check-base-images.outputs.outdated
         run: |
-          echo "${{ matrix.version }}" >> rebuild-ee-${{ matrix.version }}
+          echo "${{ matrix.version }}" >> rebuild-EE-${{ matrix.version }}
         # GitHub doesn't support outputs of matrix jobs - https://github.com/orgs/community/discussions/26639
         # Instead, write the content to artifact(s) and upload those to consume downstream