aux/trace: delete GALLIUM_TRACE_NIR log message

this is not only annoying, it breaks trace xml output

cc: mesa-stable

Acked-by: Simon Zeni <simon@bl4ckb0ne.ca>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21609>
(cherry picked from commit f99eab23ad)

.pick_status.json

@@ -5251,7 +5251,7 @@
         "description": "aux/trace: delete GALLIUM_TRACE_NIR log message",
         "nominated": true,
         "nomination_type": 0,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": null
     },

src/gallium/auxiliary/driver_trace/tr_dump.c

@@ -663,12 +663,6 @@ void trace_dump_nir(void *nir)
       return;
    }
 
-   if ((nir_count--) == 0) {
-      fputs("<string>Set GALLIUM_TRACE_NIR to a sufficiently big number "
-            "to enable NIR shader dumping.</string>", stream);
-      return;
-   }
-
    // NIR doesn't have a print to string function.  Use CDATA and hope for the
    // best.
    if (stream) {