Remove end-of-life CentOS 6 workflows. (#8121)

.github/workflows/ci.yml

@@ -58,13 +58,3 @@ jobs:
       run: |
         yum -y install gcc make
         make REDIS_CFLAGS='-Werror'
-
-  build-centos6-jemalloc:
-    runs-on: ubuntu-latest
-    container: centos:6
-    steps:
-    - uses: actions/checkout@v1
-    - name: make
-      run: |
-        yum -y install gcc make
-        make

.github/workflows/daily.yml

@@ -137,28 +137,6 @@ jobs:
     - name: cluster tests
       run: ./runtest-cluster
 
-  test-centos6-jemalloc:
-    runs-on: ubuntu-latest
-    if: github.repository == 'redis/redis'
-    container: centos:6
-    timeout-minutes: 14400
-    steps:
-    - uses: actions/checkout@v1
-    - name: make
-      run: |
-        yum -y install gcc make
-        make
-    - name: test
-      run: |
-        yum -y install which tcl util-linux-ng
-        ./runtest --accurate --verbose
-    - name: module api test
-      run: ./runtest-moduleapi --verbose
-    - name: sentinel tests
-      run: ./runtest-sentinel
-    - name: cluster tests
-      run: ./runtest-cluster
-
   test-centos7-tls:
     runs-on: ubuntu-latest
     if: github.repository == 'redis/redis'