Use ubuntu 20.04 in CI

Author: Heliozoa

.github/workflows/upload-binaries.yml

@@ -10,7 +10,7 @@ env:
 
 jobs:
   linux:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     strategy:
       matrix:
         target: [x86_64-unknown-linux-gnu]