Revert "add precompiled 2.11.0"

This reverts commit 36ec1032741874aec9ce97c4d886c3208af7ce5a.

This 2.11.0 dependency was causing issues with older sbt launchers
attempting to use the 2.11.0 scala release for sbt's classloader,
leading to binary incompatibility issues.
Merge pull request #1296 from sbt/wip/revert-scala-2.11

Revert "add precompiled 2.11.0"