[code coverage] Change log warning to info

Will ssh to bot if still nothing printed.

Bug: 1027818
Change-Id: I98147da43689d2b4ea9db0ee8643312eac6fc72b
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1935860
Auto-Submit: Yun Liu <yliuyliu@google.com>
Commit-Queue: Yuke Liao <liaoyuke@chromium.org>
Reviewed-by: Yuke Liao <liaoyuke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719180}

testing/merge_scripts/code_coverage/merge_lib.py

@@ -179,7 +179,7 @@ def _validate_and_convert_profraw(profraw_file, output_profdata_files,
     else:
       profile_valid = True
   except subprocess.CalledProcessError as error:
-    logging.warning('Validating and converting %r to %r failed with output: %r',
+    logging.info('Validating and converting %r to %r failed with output: %r',
                  profraw_file, output_profdata_file, error.output)
     validation_output = error.output