bump actions ubuntu version

Author: jepler

.github/workflows/build.yml

@@ -8,7 +8,7 @@ on: [pull_request, push]
 
 jobs:
   test:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
     - name: Dump GitHub context
       env:

.github/workflows/release.yml

@@ -10,7 +10,7 @@ on:
 
 jobs:
   upload-release-assets:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
     - name: Dump GitHub context
       env:
@@ -58,7 +58,7 @@ jobs:
         github-token: ${{ secrets.GITHUB_TOKEN }}
 
   upload-pypi:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
     - uses: actions/checkout@v1
     - name: Check For setup.py