Add missing test input

Author: aschwaighofer

test/IRGen/Inputs/relative_protocol_witness_tables2.swift

@@ -0,0 +1,15 @@
+public protocol ResilientProto {
+  associatedtype T
+  func impl()
+}
+
+
+public struct ResilientStruct<T> : ResilientProto {
+  var x : T?
+  public init(_ t: T) {
+      x = t
+  }
+  public func impl() {
+    print(x)
+  }
+}