ci: test on NumPy + Python 3.9 (#2628)

.github/workflows/labeler.yml

@@ -14,7 +14,7 @@ jobs:
         sync-labels: true
 
     - uses: actions/labeler@main
-      if: "github.event.action == 'closed' && github.event.pull_request.merged == true"
+      if: "github.event.type == 'closed' && github.event.pull_request.merged == true"
       with:
         repo-token: ${{ secrets.GITHUB_TOKEN }}
         configuration-path: .github/labeler_merged.yml

tests/requirements.txt

 --extra-index-url https://antocuni.github.io/pypy-wheels/manylinux2010/
 numpy==1.16.6; python_version<"3.6" and sys_platform!="win32"
 numpy==1.18.0; platform_python_implementation=="PyPy" and sys_platform=="darwin" and python_version>="3.6"
-numpy==1.19.1; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version>="3.6" and python_version<"3.9"
+numpy==1.19.3; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version>="3.6" and python_version<"3.10"
 pytest==4.6.9; python_version<"3.5"
 pytest==5.4.3; python_version>="3.5"
 scipy==1.2.3; (platform_python_implementation!="PyPy" or sys_platform=="linux") and python_version<"3.6"