Update sbt-test-agent to 1.9.9

Author: tgodzik

build.sc

@@ -62,7 +62,7 @@ object Dependencies {
   def nailgun                = ivy"io.github.alexarchambault.bleep:nailgun-server:1.0.7"
   def osLib                  = ivy"com.lihaoyi::os-lib:0.9.0"
   def pprint                 = ivy"com.lihaoyi::pprint:0.8.1"
-  def sbtTestAgent           = ivy"org.scala-sbt:test-agent:1.9.8"
+  def sbtTestAgent           = ivy"org.scala-sbt:test-agent:1.9.9"
   def sbtTestInterface       = ivy"org.scala-sbt:test-interface:1.0"
   def scalaDebugAdapter      = ivy"ch.epfl.scala::scala-debug-adapter:4.0.1"
   def scalaJsLinker1         = ivy"org.scala-js::scalajs-linker:$scalaJs1Version"