Update presubmit.yml per review comments

This will be picked up in the next BCR release. Switch macos to
macos_arm64. Also add 9.x and drop 7.x from the testing matrix. (We're
already not testing 7.x on CI and 7.x is out of oss-policies-info.)

Change-Id: I5d5a701034a5ba460b3eca5ee6d59bc857870dd8
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/104448
Presubmit-BoringSSL-Verified: boringssl-scoped@luci-project-accounts.iam.gserviceaccount.com <boringssl-scoped@luci-project-accounts.iam.gserviceaccount.com>
Commit-Queue: Lily Chen <chlily@google.com>
Auto-Submit: David Benjamin <davidben@google.com>
Reviewed-by: Lily Chen <chlily@google.com>

.bcr/presubmit.yml

diff --git a/.bcr/presubmit.yml b/.bcr/presubmit.yml
index 30f5c86..7294070 100644
--- a/.bcr/presubmit.yml
+++ b/.bcr/presubmit.yml
@@ -6,7 +6,7 @@
   linux_platforms:
     - debian11
     - ubuntu2204
-  bazel: [7.x, 8.x, rolling]
+  bazel: [8.x, 9.x, rolling]
 tasks:
   verify_targets_on_linux:
     name: Verify build targets on Linux
@@ -25,7 +25,7 @@
   # Work around https://github.com/bazelbuild/bazel/issues/10472
   verify_targets_on_macos:
     name: Verify build targets on macOS
-    platform: macos
+    platform: macos_arm64
     bazel: ${{ bazel }}
     build_targets: *build_targets
     build_flags: &macos_workaround
@@ -54,7 +54,7 @@
     # Work around https://github.com/bazelbuild/bazel/issues/10472
     run_test_module_on_macos:
       name: Run test module on macOS
-      platform: macos
+      platform: macos_arm64
       bazel: ${{ bazel }}
       build_targets:
         - //...