Fix GHA CI matrix evaluation value.

Author: grafikrobot

.github/workflows/ci.yml

@@ -33,7 +33,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        include: fromJSON(needs.cpp-matrix.outputs.matrix)
+        include: ${{ fromJSON(needs.cpp-matrix.outputs.matrix) }}
 
     # use matrix entries
     name: ${{ matrix.name }}