closes bpo-42029: Remove dynload_dl (GH-22687)

All references to this dynamic loading method were removed in b9949db,
when support for this method was dropped, but the implementation code
was not dropped (seemingly in oversight).
diff --git a/Python/dynload_dl.c b/Python/dynload_dl.c
deleted file mode 100644
index 2bec645..0000000
--- a/Python/dynload_dl.c
+++ /dev/null
@@ -1,23 +0,0 @@
-
-/* Support for dynamic loading of extension modules */
-
-#include "dl.h"
-
-#include "Python.h"
-#include "importdl.h"
-
-
-extern char *Py_GetProgramName(void);
-
-const char *_PyImport_DynLoadFiletab[] = {".o", NULL};
-
-
-dl_funcptr _PyImport_FindSharedFuncptr(const char *prefix,
-                                       const char *shortname,
-                                       const char *pathname, FILE *fp)
-{
-    char funcname[258];
-
-    PyOS_snprintf(funcname, sizeof(funcname), "%.20s_%.200s", prefix, shortname);
-    return dl_loadmod(Py_GetProgramName(), pathname, funcname);
-}