Standardize warnings with WARNING ⚠️ ... (#9467)

* Standardize warnings

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

segment/val.py

@@ -345,7 +345,7 @@ def run(
     pf = '%22s' + '%11i' * 2 + '%11.3g' * 8  # print format
     LOGGER.info(pf % ("all", seen, nt.sum(), *metrics.mean_results()))
     if nt.sum() == 0:
-        LOGGER.warning(f'WARNING: no labels found in {task} set, can not compute metrics without labels ⚠️')
+        LOGGER.warning(f'WARNING ⚠️ no labels found in {task} set, can not compute metrics without labels')
 
     # Print results per class
     if (verbose or (nc < 50 and not training)) and nc > 1 and len(stats):
@@ -438,9 +438,9 @@ def main(opt):
 
     if opt.task in ('train', 'val', 'test'):  # run normally
         if opt.conf_thres > 0.001:  # https://github.com/ultralytics/yolov5/issues/1466
-            LOGGER.info(f'WARNING: confidence threshold {opt.conf_thres} > 0.001 produces invalid results ⚠️')
+            LOGGER.warning(f'WARNING ⚠️ confidence threshold {opt.conf_thres} > 0.001 produces invalid results')
         if opt.save_hybrid:
-            LOGGER.info('WARNING: --save-hybrid will return high mAP from hybrid labels, not from predictions alone ⚠️')
+            LOGGER.warning('WARNING ⚠️ --save-hybrid returns high mAP from hybrid labels, not from predictions alone')
         run(**vars(opt))
 
     else: