Fix typo

Co-authored-by: greptile-apps[bot] <165735046+greptile-apps[bot]@users.noreply.github.com>

Author: amaslenn

doc/index.md

@@ -45,7 +45,7 @@ These schemas enable CloudAI to be flexible and compatible with different system
 ## CloudAI Modes Usage Examples
 
 Global options for `cloudai` command:
-- `--log-file <path>`: specify a file to log output, be default `debug.log` in the current directory is used. Contains log entries of level `DEBUG` and higher.
+- `--log-file <path>`: specify a file to log output, by default `debug.log` in the current directory is used. Contains log entries of level `DEBUG` and higher.
 - `--log-level <level>`: specify logging level for standard output, default is `INFO`.
 
 (run)=