Revert "vm_dump.c: Do not show C backtrace on riscv"

This reverts commit 6985bfb72c.

Now it should work on riscv by the previous commit. [Bug #17609]

vm_dump.c

@@ -756,7 +756,7 @@ rb_print_backtrace(void)
 #define MAX_NATIVE_TRACE 1024
     static void *trace[MAX_NATIVE_TRACE];
     int n = (int)backtrace(trace, MAX_NATIVE_TRACE);
-#if (defined(USE_ELF) || defined(HAVE_MACH_O_LOADER_H)) && defined(HAVE_DLADDR) && !defined(__sparc) && !defined(__riscv)
+#if (defined(USE_ELF) || defined(HAVE_MACH_O_LOADER_H)) && defined(HAVE_DLADDR) && !defined(__sparc)
     rb_dump_backtrace_with_lines(n, trace);
 #else
     char **syms = backtrace_symbols(trace, n);