Twitter: Update Finagle/Finatra library versions (#6308)

frameworks/Scala/finagle/build.sbt

@@ -1,4 +1,4 @@
-lazy val finagleVersion = "20.12.0"
+lazy val finagleVersion = "21.1.0"
 
 name := "finagle-benchmark"
 scalaVersion := "2.12.8"

frameworks/Scala/finatra/build.sbt

@@ -1,4 +1,4 @@
-lazy val finatraVersion = "20.12.0"
+lazy val finatraVersion = "21.1.0"
 
 name := "techempower-benchmarks-finatra"
 organization := "com.twitter"