Update CI to use Ubuntu 24.04.

Author: paciorek

.github/workflows/ci.yaml

@@ -26,8 +26,8 @@ jobs:
         config:
           - {os: windows-latest, r: 'release'}
           - {os: macOS-latest, r: 'release'}
-          - {os: ubuntu-20.04, r: 'devel', rspm: "https://packagemanager.rstudio.com/cran/__linux__/focal/latest"}
-          - {os: ubuntu-20.04, r: 'release', rspm: "https://packagemanager.rstudio.com/cran/__linux__/focal/latest"}
+          - {os: ubuntu-24.04, r: 'devel', rspm: "https://packagemanager.rstudio.com/cran/__linux__/noble/latest"}
+          - {os: ubuntu-24.04, r: 'release', rspm: "https://packagemanager.rstudio.com/cran/__linux__/noble/latest"}
 
 
     env: