Apparently Ubuntu 20 is no longer a thing (#349)

Author: deplinenoise

.github/workflows/auto-release.yml

@@ -8,7 +8,7 @@ on:
 jobs:
   tagged-release:
     name: "Tagged Release"
-    runs-on: "ubuntu-20.04"
+    runs-on: "ubuntu-latest"
 
     steps:
       - uses: actions/checkout@v2

.github/workflows/build.yml

@@ -6,7 +6,7 @@ jobs:
     strategy:
       matrix:
         checked: [no, yes]
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
         with:
@@ -16,7 +16,7 @@ jobs:
       - run: sudo cpanm File::Slurp Digest::MD5
       - run: make CHECKED=${{ matrix.checked }} all run-all-tests
   build-windows:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
         with: