Update scalatest to 3.2.0 (#68)

Author: scala-steward

build.sbt

@@ -23,7 +23,7 @@ lazy val exercises = (project in file("."))
       "joda-time"                   % "joda-time"                   % "2.10.6",
       "com.47deg"                  %% "scalacheck-toolbox-datetime" % "0.3.5",
       "com.chuusai"                %% "shapeless"                   % "2.3.3",
-      "org.scalatest"              %% "scalatest"                   % "3.1.2",
+      "org.scalatest"              %% "scalatest"                   % "3.2.0",
       "org.scalacheck"             %% "scalacheck"                  % "1.14.3",
       "org.scalatestplus"          %% "scalacheck-1-14"             % "3.1.2.0",
       "com.github.alexarchambault" %% "scalacheck-shapeless_1.14"   % "1.2.5"