Change ubuntu version

.github/workflows/publish.yml

@@ -10,7 +10,7 @@ on:
 jobs:
   test-package:
     timeout-minutes: 20
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2

.github/workflows/release.yml

@@ -10,7 +10,7 @@ on:
 jobs:
   test-package:
     timeout-minutes: 20
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2