Update scalatest to 3.1.0 (#94)

Author: scala-steward

project/Dependencies.scala

@@ -4,5 +4,5 @@ object Library {
   val classgraph = "io.github.classgraph"  % "classgraph"  % "4.8.57"
   val jtidy      = "net.sf.jtidy"          % "jtidy"       % "r938"
   val sbtParadox = "com.lightbend.paradox" % "sbt-paradox" % "0.6.7"
-  val scalatest  = "org.scalatest"         %% "scalatest"  % "3.0.8"
+  val scalatest  = "org.scalatest"         %% "scalatest"  % "3.1.0"
 }

src/test/scala/com/lightbend/paradox/apidoc/MarkdownBaseSpec.scala

@@ -19,15 +19,16 @@ package com.lightbend.paradox.apidoc
 import com.lightbend.paradox.tree.Tree.{Forest, Location}
 import java.io.{File, PrintWriter}
 
-import org.scalatest.{FlatSpec, Matchers}
 import com.lightbend.paradox.template.PageTemplate
 import com.lightbend.paradox.PrintlnLogger
 import com.lightbend.paradox.ThrowingErrorContext
 import java.nio.file._
 
 import com.lightbend.paradox.markdown._
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
 
-abstract class MarkdownBaseSpec extends FlatSpec with Matchers {
+abstract class MarkdownBaseSpec extends AnyFlatSpec with Matchers {
   val markdownReader = new Reader
   val markdownWriter = new Writer