[test] Temporarily disable PatternMatching prototype under optimization. (#5822)

Issue tracked by rdar://problem/29289360.

Author: jrose-apple

Diff for: test/Prototypes/PatternMatching.swift

@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 // RUN: %target-run-simple-swift
 // REQUIRES: executable_test
+// REQUIRES: swift_test_mode_optimize_none
 
 //===--- Niceties ---------------------------------------------------------===//
 typealias Element_<S: Sequence> = S.Iterator.Element