Remove thread limitation from GHA runner

Author: mborland

.github/workflows/ci.yml

@@ -70,7 +70,7 @@ jobs:
         run: ./config_info_travis
         working-directory: ../boost-root/libs/config/test
       - name: Test
-        run: ../../../b2 -j2 toolset=$TOOLSET ${{ matrix.suite }} define=CI_SUPPRESS_KNOWN_ISSUES define=SLOW_COMPILER
+        run: ../../../b2 toolset=$TOOLSET ${{ matrix.suite }} define=CI_SUPPRESS_KNOWN_ISSUES define=SLOW_COMPILER
         working-directory: ../boost-root/libs/math/test
   ubuntu-focal-no-eh:
     runs-on: ubuntu-20.04