Cygwin: multiple_cygwin_problem: drop obsolete check for "cygheap"

After decoupling cygheap from the DLL loading address, the check
for a different _cygheap_start has gone.  So the matching string
check in multiple_cygwin_problem is obsolete now.

Fixes: 2f9b8ff00c ("Cygwin: decouple cygheap from Cygwin DLL")
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/dcrt0.cc

@@ -1262,7 +1262,7 @@ api_fatal (const char *fmt, ...)
 void
 multiple_cygwin_problem (const char *what, uintptr_t magic_version, uintptr_t version)
 {
-  if (_cygwin_testing && (strstr (what, "proc") || strstr (what, "cygheap")))
+  if (_cygwin_testing && (strstr (what, "proc")))
     {
       child_proc_info->type = _CH_WHOOPS;
       return;