fix warning in build.sbt

[xuwei-k]

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Fixes

Fixes warning in build.sbt

Purpose

Background Context

/home/travis/build/playframework/anorm/build.sbt:54: warning: method copy in class AssemblyOption is deprecated (since 1.0.0): copy method is deprecated; use withIncludeBin(...) etc
    _.copy(includeScala = false) // java libraries shouldn't include scala
      ^

References

sbt/sbt-assembly#433