fix example MODULE.bazel comment

Author: sluongng

examples/bzlmod/MODULE.bazel

@@ -48,7 +48,10 @@ buildbuddy = use_extension("@toolchains_buildbuddy//:extensions.bzl", "buildbudd
 # (Optional) Use the repository directly instead.
 #     use_repo(buildbuddy, "buildbuddy_toolchain")
 
-# Register the toolchains explicitly
+# Register the toolchains with higher priority than dependent modules (i.e. rules_cc)
+#
+# User may explicitly choose a specific toolchain using the `--extra_toolchains=` flag.
+# See 'examples/bzlmod/.bazelrc' file for more details.
 register_toolchains(
     "@toolchains_buildbuddy//toolchains/cc:all",
 )