V126-011 Fix compilation warnings of GCC 11

Change-Id: I6bf66badff9ab6197c73297970cccc5e62e0ce7f

Author: reznikmm

src/gnatcoll-io-remote.adb

@@ -851,6 +851,7 @@ package body GNATCOLL.IO.Remote is
       end case;
 
       GNAT.OS_Lib.Delete_File (String (Tmp) & File.Tmp_Name, Dead);
+      pragma Assert (Dead, "couldn't delete temp file");
    end Close;
 
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