Have scripts/update_deps.py update bazel pin

[pgmoka]

Currently scripts/update_deps.py does not update bazel version. We should consider changing this to make sure pin updates done weekly also update bazel.

[zhanyong-wan]

Is there a need to update bazel frequently?

Usually we don't update the toolchain unless we need to get specific bug fixes or features. While we can try to automate the update of bazel versions, I think it should be a separate command.