[CI] Remove the CentOs tests as vae23 and 24 stable + frequent failure

Rational:
- was introduced because bare-metal OS on virgo and virgo2 is centOS + debian containers were not immediately available stable
- now both vae23 (debian10) and vae24 (debian11) are available and well established/used by CBM virgo users
- these two jobs were responsible for ~50% of all pipeline failures due to something hanging up in the load_libraries test at a cost of 2 x 900 s

.gitlab-ci.yml

@@ -269,24 +269,6 @@ FileLicenceCheck:
   tags:
     - CbmRoot_apptainer
 
-.apptainer_centos7_variables_apr21: &apptainer_centos7_variables_apr21
-    OS: centos7
-    FAIRSOFT_VERSION: apr21p2
-    FAIRROOT_VERSION: v18.6.7
-    BASE_PATH: "/cvmfs/fairsoft.gsi.de/$OS/gcc8"
-    SIMPATH: "$BASE_PATH/fairsoft/$FAIRSOFT_VERSION"
-    FAIRROOTPATH: "$BASE_PATH/fairroot/${FAIRROOT_VERSION}_fs_${FAIRSOFT_VERSION}"
-    CONFIGFILE: "/cvmfs/cbm.gsi.de/$OS/bin/setup_development_environment_test.sh"
-
-.apptainer_centos7_variables_nov22p1: &apptainer_centos7_variables_nov22p1
-    OS: centos7
-    FAIRSOFT_VERSION: nov22p1
-    FAIRROOT_VERSION: v18.8.0
-    BASE_PATH: "/cvmfs/fairsoft.gsi.de/$OS/gcc8"
-    SIMPATH: "$BASE_PATH/fairsoft/$FAIRSOFT_VERSION"
-    FAIRROOTPATH: "$BASE_PATH/fairroot/${FAIRROOT_VERSION}_${FAIRSOFT_VERSION}"
-    CONFIGFILE: "/cvmfs/fairsoft.gsi.de/$OS/bin/setup_development_environment.sh"
-
 .apptainer_vae23_variables_apr21: &apptainer_vae23_variables_apr21
     CONTAINER: "/cvmfs/vae.gsi.de/vae23/containers/user_container-production.sif"
     OS: vae23
@@ -455,16 +437,6 @@ CbmRoot_Merge_Apptainer_debian11_apr21:
   variables:
     <<: [*mergeRequestVariables, *apptainer_debian11_variables_apr21]
 
-CbmRoot_Merge_Apptainer_centos7_apr21:
-  <<: [*apptainer_tag, *check_merge_request, *build_and_test]
-  variables:
-    <<: [*mergeRequestVariables, *apptainer_centos7_variables_apr21]
-
-CbmRoot_Merge_Apptainer_centos7_nov22p1:
-  <<: [*apptainer_tag, *check_merge_request, *build_and_test]
-  variables:
-    <<: [*mergeRequestVariables, *apptainer_centos7_variables_nov22p1]
-
 CbmRoot_Merge_Apptainer_vae23_apr21:
   <<: [*apptainer_tag, *check_merge_request, *build_and_test]
   variables: