Remove another obsolete Borland hdrstop pragma

See f57f214122 (Remove BCC-specific hdrstop pragma from everywhere,
2020-10-12).

tests/net/webrequest.cpp

@@ -13,10 +13,6 @@
 
 #include "testprec.h"
 
-#ifdef __BORLANDC__
-#pragma hdrstop
-#endif
-
 #ifndef WX_PRECOMP
     #include "wx/wx.h"
 #endif // WX_PRECOMP