science/libtensorflow1: disallow newer Bazel

Does not build with newer Bazel:

Repository rule git_repository defined at:

/usr/ports/science/libtensorflow1/work-default/bazel_out/98e92f9393bc83ca8c28c921fe93f245/external/bazel_tools/tools/build_defs/repo/git.bzl:199:33: in <toplevel>

ERROR: /usr/ports/science/libtensorflow1/work-default/bazel_out/98e92f9393bc83ca8c28c921fe93f245/external/io_bazel_rules_docker/container/image.bzl:550:31: invalid escape sequence: \s. Use '\\' to insert '\'.

PR: ports/260694
Discovered by: Dario <darioml@gmail.com>