Remove an old, seemingly out of date, comment.

The referenced script no longer seems to exist.

llvm-svn: 192848

clang/test/Preprocessor/predefined-arch-macros.c

@@ -1,6 +1,3 @@
-// These tests are generated by running utils/generate_arch_predefine_tests.sh
-// to observe GCC's behavior (or some other system compiler's behavior).
-//
 // Begin X86/GCC/Linux tests ----------------
 //
 // RUN: %clang -march=i386 -m32 -E -dM %s -o - 2>&1 \