Use latest gha rcmdcheck standard

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

-# NOTE: This workflow is overkill for most R packages
-# check-standard.yaml is likely a better choice
-# usethis::use_github_action("check-standard") will install it.
-#
-# For help debugging build failures open an issue on the RStudio community with the 'github-actions' tag.
-# https://community.rstudio.com/new-topic?category=Package%20development&tags=github-actions
+# Workflow derived from https://github.com/r-lib/actions/tree/v2/examples
+# Need help debugging build failures? Start at https://github.com/r-lib/actions#where-to-find-help
 on:
   push:
-    branches:
-      - main
+    branches: [main, master]
   pull_request:
-    branches:
-      - main
+    branches: [main, master]
 
 name: R-CMD-check
 
         config:
           - {os: macOS-latest,   r: 'release'}
           - {os: windows-latest, r: 'release'}
-          - {os: windows-latest, r: '3.6'}
-          - {os: ubuntu-18.04,   r: 'devel', http-user-agent: 'release'}
-          - {os: ubuntu-18.04,   r: 'release'}
-          - {os: ubuntu-18.04,   r: 'oldrel-1'}
+          - {os: ubuntu-latest,  r: 'devel', http-user-agent: 'release'}
+          - {os: ubuntu-latest,  r: 'release'}
+          - {os: ubuntu-latest,  r: 'oldrel-1'}
 
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
     steps:
       - uses: actions/checkout@v2
 
-      - uses: r-lib/actions/setup-r@v1
-        id: install-r
+      - uses: r-lib/actions/setup-pandoc@v2
+
+      - uses: r-lib/actions/setup-r@v2
         with:
           r-version: ${{ matrix.config.r }}
           http-user-agent: ${{ matrix.config.http-user-agent }}
           use-public-rspm: true
 
-      - uses: r-lib/actions/setup-pandoc@v1
-
-      - name: Install devel system dependencies
-        if: matrix.config.os == 'ubuntu-18.04' && matrix.config.r == 'devel'
-        run: sudo apt-get install -y libcurl4-openssl-dev
-
-      - uses: r-lib/actions/setup-r-dependencies@v1
+      - uses: r-lib/actions/setup-r-dependencies@v2
         with:
-          cache-version: 1
-          extra-packages: rcmdcheck
-
-      - uses: r-lib/actions/check-r-package@v1
-
-      - name: Show testthat output
-        if: always()
-        run: find check -name 'testthat.Rout*' -exec cat '{}' \; || true
-        shell: bash
-
-      - name: Code coverage
-        if: matrix.config.os == 'macOS-latest' && matrix.config.r == 'release'
-        shell: Rscript {0}
-        run: |
-          pak::pkg_install("covr")
-          covr::codecov()
+          extra-packages: any::rcmdcheck
+          needs: check
 
-      - name: Upload check results
-        if: failure()
-        uses: actions/upload-artifact@main
+      - uses: r-lib/actions/check-r-package@v2
         with:
-          name: ${{ matrix.config.os }}-r${{ matrix.config.r }}-results
-          path: check
+          upload-snapshots: true