Disable this test, which is failing in some branches.

Author: rudkx

validation-test/Sema/type_checker_perf/fast/rdar32999041.swift.gyb

@@ -1,6 +1,8 @@
 // RUN: %scale-test --begin 3 --end 8 --step 1 --select incrementScopeCounter %s
 // REQUIRES: OS=macosx
 // REQUIRES: asserts
+// FIXME: https://bugs.swift.org/browse/SR-6997
+// REQUIRES: SR6997
 
 _ = MemoryLayout<Int>.size
 %for i in range(0, N):