[gh-actions] potential fix

Author: hbaniecki

.github/workflows/R-CMD-check.yaml

@@ -42,9 +42,9 @@ jobs:
           - {os: windows-latest, r: '4.1'}
           - {os: windows-latest, r: '4.0'}
           - {os: windows-latest, r: '3.6'}
-          - {os: ubuntu-18.04, r: '4.1', rspm: "https://demo.rstudiopm.com/all/__linux__/xenial/latest"}
-          - {os: ubuntu-18.04, r: '4.0', rspm: "https://demo.rstudiopm.com/all/__linux__/xenial/latest"}
-          - {os: ubuntu-18.04, r: '3.6', rspm: "https://demo.rstudiopm.com/all/__linux__/xenial/latest"}
+          - {os: ubuntu-18.04, r: '4.1', vdiffr: true,  xref: true, rspm: "https://packagemanager.rstudio.com/cran/__linux__/bionic/latest"}
+          - {os: ubuntu-18.04, r: '4.0', vdiffr: true,  xref: true, rspm: "https://packagemanager.rstudio.com/cran/__linux__/bionic/latest"}
+          - {os: ubuntu-18.04, r: '3.6', vdiffr: true,  xref: true, rspm: "https://packagemanager.rstudio.com/cran/__linux__/bionic/latest"}
 
     env:
       R_REMOTES_NO_ERRORS_FROM_WARNINGS: true