[ci] use flag '--allow-releaseinfo-change' in some 'apt-get update' calls (#4524)

* [ci] prefer 'apt update' to 'apt-get update' in some R builds

* use --allow-releaseinfo-change

.github/workflows/r_package.yml

@@ -181,7 +181,7 @@ jobs:
       - name: Install Git before checkout
         shell: bash
         run: |
-          apt-get update
+          apt-get update --allow-releaseinfo-change
           apt-get install --no-install-recommends -y git
       - name: Checkout repository
         uses: actions/checkout@v2.3.4
@@ -210,7 +210,7 @@ jobs:
       - name: Install Git before checkout
         shell: bash
         run: |
-          apt-get update
+          apt-get update --allow-releaseinfo-change
           apt-get install --no-install-recommends -y git
       - name: Checkout repository
         uses: actions/checkout@v2.3.4