[nfc] [cxx-interop] Enable method tests on windows.

Author: zoecarver

test/Interop/Cxx/templates/member-templates.swift

@@ -1,9 +1,6 @@
 // RUN: %target-run-simple-swift(-I %S/Inputs -Xfrontend -enable-cxx-interop)
 //
 // REQUIRES: executable_test
-//
-// We can't yet call member functions correctly on Windows (SR-13129).
-// XFAIL: OS=windows-msvc
 
 import MemberTemplates
 import StdlibUnittest