finagle/finatra: Update to 19.1.0 release. (#4349)

This commit updates the Finagle and Finatra versions used for benchmarks from 18.12.0 to 19.1.0,
which is now the latest version.

frameworks/Scala/finagle/build.sbt

@@ -1,4 +1,4 @@
-lazy val finagleVersion = "18.12.0"
+lazy val finagleVersion = "19.1.0"
 
 name := "finagle-benchmark"
 scalaVersion := "2.12.5"

frameworks/Scala/finatra/build.sbt

@@ -1,4 +1,4 @@
-lazy val finatraVersion = "18.12.0"
+lazy val finatraVersion = "19.1.0"
 
 name := "techempower-benchmarks-finatra"
 organization := "com.twitter"