Run primer in single-threaded mode to reduce memory usage

Author: George-Ogden

.github/workflows/mypy_primer.yml

@@ -55,6 +55,7 @@ jobs:
             --num-shards 10 --shard-index ${{ matrix.shard-index }} \
             --debug \
             --output concise \
+            -j 1 \
             | tee diff_${{ matrix.shard-index }}.txt
           ) || [ $? -eq 1 ]
       - if: ${{ matrix.shard-index == 0 }}