presubmit.yml: Use xcode 14.2

It appears the upgrade to xcode 14.3 broke the macos build on builkite.
The last good build was using xcode 14.2, so go back to this version
until the issue is resolved.

.bazelci/presubmit.yml

@@ -31,6 +31,7 @@ platforms:
     test_targets:
     - "//..."
   macos:
+    xcode_version: "14.2"
     build_targets:
     - "//..."
     test_targets: