Remove --cpu=darwin_arm64 flag for Apple Silicon build

Since we already use actual Apple Silicon machines on CI, we don't need cross compile Bazel anymore.

See bazelbuild/continuous-integration#1495

RELNOTES: None
PiperOrigin-RevId: 489548332
Change-Id: Ia9f6b43686fb91714bc3e6620eadf3c6a780d565

.bazelci/build_bazel_binaries.yml

@@ -37,9 +37,6 @@ platforms:
     build_flags:
       - "-c"
       - "opt"
-      # TODO(pcloudy): Remove the following flag when we actually use Apple
-      # Silicon machines for macos_arm64 platform
-      - "--cpu=darwin_arm64"
   windows:
     build_flags:
       - "--copt=-w"