update rules scala

[stmitt]

This fixes this error:

ERROR: /private/var/tmp/_bazel_stefan/e163f22b8b86a0fc6a37d2590d6618d1/external/io_bazel_rules_scala_scala_library/BUILD:9:13: in scala_import rule @@io_bazel_rules_scala_scala_library//:io_bazel_rules_scala_scala_library:
Traceback (most recent call last):
	File "/private/var/tmp/_bazel_stefan/e163f22b8b86a0fc6a37d2590d6618d1/external/io_bazel_rules_scala/scala/scala_import.bzl", line 34, column 19, in _scala_import_impl
		_stamp_jar(ctx, jar)
	File "/private/var/tmp/_bazel_stefan/e163f22b8b86a0fc6a37d2590d6618d1/external/io_bazel_rules_scala/scala/scala_import.bzl", line 12, column 33, in _stamp_jar
		return java_common.stamp_jar(
	File "/virtual_builtins_bzl/common/java/java_common.bzl", line 117, column 68, in _stamp_jar
Error in _check_java_toolchain_is_declared_on_rule: Rule 'scala_import' in '/private/var/tmp/_bazel_stefan/e163f22b8b86a0fc6a37d2590d6618d1/external/io_bazel_rules_scala_scala_library/BUILD:9:13' must declare '@@bazel_tools//tools/jdk:toolchain_type' toolchain in order to use java_common. See https://github.com/bazelbuild/bazel/issues/18970.
ERROR: /private/var/tmp/_bazel_stefan/e163f22b8b86a0fc6a37d2590d6618d1/external/io_bazel_rules_scala_scala_library/BUILD:9:13: Analysis of target '@@io_bazel_rules_scala_scala_library//:io_bazel_rules_scala_scala_library' failed
ERROR: Analysis of target '//src:djinni' failed; build aborted: Analysis failed
INFO: Elapsed time: 0.066s, Critical Path: 0.00s
INFO: 1 process: 1 internal.
ERROR: Build did NOT complete successfully