remove now-unnecessary memory-based parallelism limiting

.forgejo/workflows/test.yml

@@ -70,12 +70,4 @@ jobs:
       - uses: https://github.com/Swatinem/rust-cache@v2
         with:
           save-if: ${{ github.ref == 'refs/heads/master' }}
-      - run: |
-          avail_mem="$(free -b | awk '/^Mem:/{print($2)}')"
-          # estimate that each test needs 16GiB
-          ((par_from_mem = avail_mem / (16 << 30)))
-          par="$(nproc)"
-          if ((par_from_mem > 0 && par > par_from_mem)); then
-              par="$par_from_mem"
-          fi
-          cargo test -- --test-threads="$par"
+      - run: cargo test