Fix `LINUX_BINARY_PLATFORM` (#1914)

Addressing downstream breakage:
https://buildkite.com/bazel/bazel-at-head-plus-downstream/builds/3713#018e30d8-e37e-491c-b58e-f54ef9170a01

Due to
https://github.com/bazelbuild/bazel/commit/63dcbfbe6556ff52518cacd5ae943183bfe9a171
diff --git a/buildkite/bazelci.py b/buildkite/bazelci.py
index 73e4685..6d4f6e7 100755
--- a/buildkite/bazelci.py
+++ b/buildkite/bazelci.py
@@ -593,7 +593,7 @@
 # In order to test that "the one Linux binary" that we build for our official releases actually
 # works on all Linux distributions that we test on, we use the Linux binary built on our official
 # release platform for all Linux downstream tests.
-LINUX_BINARY_PLATFORM = "centos7_java11_devtoolset10"
+LINUX_BINARY_PLATFORM = "centos7"
 
 XCODE_VERSION_REGEX = re.compile(r"^\d+\.\d+(\.\d+)?$")
 XCODE_VERSION_OVERRIDES = {"10.2.1": "10.3", "11.2": "11.2.1", "11.3": "11.3.1"}