[nfc] Enable member function templates silgen test.

This test was dissabled until swiftlang#30630 (support calling C++ constructors)
landed. That patch landed a while ago, so this test should be enabled.

Author: zoecarver

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

@@ -2,7 +2,6 @@
 
 // We can't yet call member functions correctly on Windows (SR-13129).
 // XFAIL: OS=windows-msvc
-// REQUIRES: fixing-after-30630
 
 import MemberTemplates