Remove outdated development remark (#303)

This is a leftover from when TSC was vendored inside SwiftPM, this hasn't been the case anymore for quite some time.

Author: neonichu

README.md

@@ -4,12 +4,6 @@ swift-tools-support-core
 Contains common infrastructural code for both [SwiftPM](https://github.com/apple/swift-package-manager)
 and [llbuild](https://github.com/apple/swift-llbuild).
 
-Development
--------------
-
-All changes to source files in this repository need to be done in the repository of the Swift Package Manager repository ([link](https://github.com/apple/swift-package-manager)) and then copied here using the Script in `Utilities/import` which takes the local path to the SwiftPM directory as input (or uses `../swiftpm` as default).
-All targets with a TSC prefix in [SwiftPM](https://github.com/apple/swift-package-manager) are part of the swift-tools-support-core and will be imported by the import script. The plan is to eventually move ownership to this repository.
-
 License
 -------