fix: Bump scala rules to a version using secure maven central

[daniellervik]

As of Jan 15th central is requiring secure connections. https://central.sonatype.org/articles/2019/Apr/30/http-access-to-repo1mavenorg-and-repomavenapacheorg-is-being-deprecated/

The errors I've seen are similar to this, that relates to the annocement:

…/external/io_bazel_rules_scala/scala/BUILD:44:1: no such package '@io_bazel_rules_scala_scala_reflect//': java.io.IOException: Error downloading [http://central.maven.org/maven2/org/scala-lang/scala-reflect/2.12.6/scala-reflect-2.12.6.jar] to …/external/io_bazel_rules_scala_scala_reflect/scala-reflect-2.12.6.jar: GET returned 501 HTTPS Required and referenced by '@io_bazel_rules_scala//scala:scalac_default'

Current scala dependency version we've pinned is using insecure connection, so it needs to be bumped e.g. to run sync-deps and format. PR discussing this issue and PR's resolving it: bazelbuild/rules_scala#920