Run web tests on 20.04

This is necessary to get Firefox to work.

Signed-off-by: Joe Richey <joerichey@google.com>

Author: josephlr

.github/workflows/tests.yml

@@ -187,7 +187,8 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - os: ubuntu-22.04
+          # Firefox isn't available on 22.04 yet, so we must use 20.04
+          - os: ubuntu-20.04
             host: x86_64-unknown-linux-musl
           - os: windows-2022
             host: x86_64-pc-windows-msvc