Silence PNG early end-of-file warning

While interesting, it does not appear this warning is useful to anyone.

libclamav/png.c

@@ -137,7 +137,7 @@ cl_error_t cli_parsepng(cli_ctx *ctx)
         if (chunk_data_length > 0) {
             ptr = (uint8_t *)fmap_need_off_once(map, offset, chunk_data_length);
             if (NULL == ptr) {
-                cli_warnmsg("PNG: Unexpected early end-of-file.\n");
+                cli_dbgmsg("PNG: Unexpected early end-of-file.\n");
                 if (SCAN_HEURISTIC_BROKEN_MEDIA) {
                     status = cli_append_potentially_unwanted(ctx, "Heuristics.Broken.Media.PNG.EOFReadingChunk");
                 }