Temporarily disable long test parse_stdlib.sil

rdar://81658645 (Swift CI: 1. OSS - Swift (Tools Opt+Assert, Stdlib
Opt+DebInfo+Assert, Long Test) - macOS (main);
parse_stdlib.sil.tmp.sil: error: expected '>' in SIL instruction)

Author: atrick

validation-test/SIL/parse_stdlib.sil

@@ -3,3 +3,4 @@
 // RUN: %target-sil-opt -enable-sil-verify-all=true %t.sil > /dev/null
 // REQUIRES: long_test
 // REQUIRES: nonexecutable_test
+// REQUIRES: rdar81658645