C++: Update test after extractor changes

Also remove incorrect FP comment. clang does not support `#pragma hdrstop` in
its non-cl-emulation mode.

Author: jketema

cpp/ql/test/header-variant-tests/clang-pch/clang-pch.expected

@@ -1,6 +1,7 @@
 | b.c:5:3:5:34 | return ... | 10 |
 | c.c:2:3:2:20 | return ... | 5 |
 | e.c:2:3:2:19 | return ... | 17 |
+| g.c:3:3:3:12 | return ... | 20 |
 | i.c:3:3:3:12 | return ... | 30 |
 | i.c:8:3:8:12 | return ... | 31 |
 | i.c:13:3:13:12 | return ... | 32 |

cpp/ql/test/header-variant-tests/clang-pch/i.c

@@ -1,6 +1,6 @@
 #ifdef SEEN_H
 static int h() {
-  return 30; // [FALSE POSITIVE] (#pragma hdrstop bug, SEEN_H should not be defined in the precompiled header)
+  return 30;
 }
 #endif
 #ifdef H1
@@ -10,7 +10,7 @@ static int h1() {
 #endif
 #ifdef H2
 static int h2() {
-  return 32; // [FALSE POSITIVE] (#pragma hdrstop bug, H2 should not be defined in the precompiled header)
+  return 32;
 }
 #endif
 // semmle-extractor-options: --clang -include-pch ${testdir}/clang-pch.testproj/h.pch