[clang] update pr27699 test to make headers different (NFC)

some build systems treat those headers as identical, causing a warning

diff --git a/clang/test/Modules/Inputs/PR27699/Subdir/b.h b/clang/test/Modules/Inputs/PR27699/Subdir/b.h
index 6c36a1a..76e62a6 100644 (file)
--- a/clang/test/Modules/Inputs/PR27699/Subdir/b.h
+++ b/clang/test/Modules/Inputs/PR27699/Subdir/b.h
@@ -1 +1,2 @@
+// Identical to a.h.
 #include "streambuf"