Remove sbt install from the end of Dockerfile

This is a Java project. There's no need for it to pre-cache sbt

.devcontainer/Dockerfile

@@ -25,15 +25,3 @@ RUN bash -c 'cs install sbt'
 
 # Get http server
 RUN bash -c 'npm install -g http-server'
-
-# Precache sbt version as part of the image.
-ARG SBT_VERSION=1.7.0
-ARG SCALA_VERSION=3.1.3
-ARG SCALAJS_VERSION=1.10.1
-RUN mkdir -p /sbtprecacheproj/project && \
-  cd /sbtprecacheproj && \
-  echo sbt.version=${SBT_VERSION} > project/build.properties && \
-  echo 'addSbtPlugin("org.scala-js" % "sbt-scalajs" % "'${SCALAJS_VERSION}'")' > project/plugins.sbt && \
-  echo '@main def hello = println("hello")' > main.scala && \
-  echo 'enablePlugins(ScalaJSPlugin); scalaVersion := "'${SCALA_VERSION}'"' > build.sbt && \
-  sbt fastLinkJS && cd / && rm -r -f /tmp/sbt-precompile