3rdparty: Actually upgrade scalatest to 3.1.2

Problem

In the previous commit where I claimed to have upgraded to 3.1.2, I actually
upgraded to 3.1.1.  I also broke the sbt build 😬

Solution

Let's actually move to 3.1.2.  We aren't moving to 3.2.0 yet because of the
breaking API changes related to suite names.

JIRA Issues: CSL-9722

Differential Revision: https://phabricator.twitter.biz/D518794

build.sbt

@@ -89,9 +89,9 @@ val baseSettings = Seq(
  // See https://www.scala-sbt.org/0.13/docs/Testing.html#JUnit
  "com.novocode" % "junit-interface" % "0.11" % "test",
  "org.mockito" % "mockito-all" % "1.10.19" % "test",
- "org.scalatest" %% "scalatest" % "3.1.1" % "test",
+ "org.scalatest" %% "scalatest" % "3.1.2" % "test",
  "org.scalatestplus" %% "junit-4-12" % "3.1.2.0" % "test",
- "org.scalatestplus" %% "mockito_1-10" % "3.1.0.0" % "test"
+ "org.scalatestplus" %% "mockito-1-10" % "3.1.0.0" % "test"
  ),
  fork in Test := true, // We have to fork to get the JavaOptions
  // Workaround for cross building HealthyQueue.scala, which is not compatible between
@@ -487,9 +487,9 @@ lazy val utilTest = Project(
  name := "util-test",
  libraryDependencies ++= Seq(
  "org.mockito" % "mockito-all" % "1.10.19",
- "org.scalatest" %% "scalatest" % "3.1.1",
+ "org.scalatest" %% "scalatest" % "3.1.2",
  "org.scalatestplus" %% "junit-4-12" % "3.1.2.0",
- "org.scalatestplus" %% "mockito_1-10" % "3.1.1.0"
+ "org.scalatestplus" %% "mockito-1-10" % "3.1.0.0"
  )
  ).dependsOn(utilCore, utilLogging)