CI configs: switch centos to centos7_java11_devtoolset10

Downstream tests can only fetch Bazel binary from
centos7_java11_devtoolset10 platform, therefore we have to make this
change to be able to test downstream projects. There is no change to
Bazel itself.

.bazelci/build_bazel_binaries.yml

@@ -1,6 +1,6 @@
 ---
 platforms:
-  centos7:
+  centos7_java11_devtoolset10:
     build_targets:
       - "//src:bazel"
       - "//src:bazel_nojdk"

.bazelci/postsubmit.yml

@@ -1,6 +1,6 @@
 ---
 tasks:
-  centos7:
+  centos7_java11_devtoolset10:
     shell_commands:
       - sed -i.bak -e 's/^# android_sdk_repository/android_sdk_repository/' -e 's/^#
         android_ndk_repository/android_ndk_repository/' WORKSPACE

.bazelci/presubmit.yml

@@ -1,6 +1,6 @@
 ---
 tasks:
-  centos7:
+  centos7_java11_devtoolset10:
     shards: 4
     shell_commands:
       - sed -i.bak -e 's/^# android_sdk_repository/android_sdk_repository/' -e 's/^#