Merge pull request swiftlang#226 from apple/clackary-patch-1

Update PULL_REQUEST_TEMPLATE.md

Author: Zachary 'Clack' Cole

.github/PULL_REQUEST_TEMPLATE.md

@@ -11,8 +11,7 @@ To be accepted into the Swift source compatibility test suite, a project must:
 - [ ] support building on either Linux or macOS
 - [ ] target Linux, macOS, or iOS/tvOS/watchOS device
 - [ ] be contained in a publicly accessible git repository
-- [ ] maintain a project branch that builds against Swift 3.0 compatibility mode
-      or Swift 4.0 and passes any unit tests
+- [ ] maintain a project branch that builds against Swift 4.0 and passes any unit tests
 - [ ] have maintainers who will commit to resolve issues in a timely manner
 - [ ] be compatible with the latest GM/Beta versions of *Xcode* and *swiftpm*
 - [ ] add value not already included in the suite