Update ci.yml

Author: Semyon1104

.github/workflows/ci.yml

@@ -51,7 +51,7 @@ jobs:
             ${{ matrix.stats && '-DENABLE_STATISTIC_TENSORS=ON' || '' }} \
             ${{ matrix.stats && '-DENABLE_STATISTIC_TIME=ON' || '' }} \
             ${{ matrix.stats && '-DENABLE_STATISTIC_WEIGHTS=ON' || '' }}
-            cmake --build build --parallel
+            cmake --build build --parallel 2
       env:
         CTEST_OUTPUT_ON_FAILURE: 1
     - name: Prepare OpenCV libs