i965/clear: Drop a stale comment in fast_clear_depth

This comment made more sense when it was above the calls to
intel_miptree_slice_set_needs_depth_resolve(). We stopped using these
functions at commit 554f7d6d02
("i965: Move depth to the new resolve functions").

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/mesa/drivers/dri/i965/brw_clear.c

@@ -228,13 +228,9 @@ brw_fast_clear_depth(struct gl_context *ctx)
       }
    }
 
-   /* Now, the HiZ buffer contains data that needs to be resolved to the depth
-    * buffer.
-    */
    intel_miptree_set_aux_state(brw, mt, depth_irb->mt_level,
                                depth_irb->mt_layer, num_layers,
                                ISL_AUX_STATE_CLEAR);
-
    return true;
 }