GHA: simplify check workflow for arm linux

No need to pass rspm input parameter now, with the
new r-lib/actions release.

[ci skip]

Author: gaborcsardi

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

@@ -34,8 +34,8 @@ jobs:
           - {os: windows-latest, r: 'oldrel-4'}
           - {os: windows-latest, r: '3.6.3'}
 
-          - {os: ubuntu-latest,  r: 'devel', http-user-agent: 'release'}
-          - {os: ubuntu-22.04-arm, r: 'release', rspm: 'no' }
+          - {os: ubuntu-latest,  r: 'devel' }
+          - {os: ubuntu-22.04-arm, r: 'release' }
           - {os: ubuntu-latest,  r: 'release'}
           - {os: ubuntu-latest,  r: 'oldrel-1'}
           - {os: ubuntu-latest,  r: 'oldrel-2'}
@@ -54,8 +54,7 @@ jobs:
       - uses: r-lib/actions/setup-r@v2
         with:
           r-version: ${{ matrix.config.r }}
-          http-user-agent: ${{ matrix.config.http-user-agent }}
-          use-public-rspm: ${{ matrix.config.rspm || 'true' }}
+          use-public-rspm: true
 
       - uses: r-lib/actions/setup-r-dependencies@v2
         with: