Remove CentOS from CI (#686)

* use vaulted centos packages

* removed centos 7 from ci

.github/workflows/ci.yml

@@ -184,23 +184,6 @@ jobs:
     - name: Test
       run: cabal test -fpure-haskell --ghc-options=-fno-ignore-asserts --enable-tests --test-show-details=direct all
 
-  old-gcc:
-    needs: build
-    runs-on: ubuntu-latest
-    container:
-      image: centos:7
-    steps:
-    - name: install deps
-      run: |
-          yum install -y gcc gmp gmp-devel make ncurses ncurses-compat-libs xz perl
-          curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | BOOTSTRAP_HASKELL_NONINTERACTIVE=1 BOOTSTRAP_HASKELL_GHC_VERSION=9.2.8 sh
-    - uses: actions/checkout@v3 #This version must stay old enough to remain compatible with the container image
-    - name: test
-      run: |
-          source ~/.ghcup/env
-          cabal update
-          cabal run bytestring-tests
-
   i386:
     needs: build
     runs-on: ubuntu-latest