Add missing -i to sed command

The release notes were missing a `-i` in the `sed` command suggested to
update the `pylint` ignore rules.

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

RELEASE_NOTES.md

@@ -15,7 +15,7 @@ To upgrade without regenerating the project, you can follow these steps:
 - Run the following command to add the new `pylint` ignore rules:
 
     ```sh
-    sed '/  # Checked by flake8/a\  "redefined-outer-name",\n  "unused-import",' pyproject.toml
+    sed '/  # Checked by flake8/a\  "redefined-outer-name",\n  "unused-import",' -i pyproject.toml
     ```
 
 - It is recommended to update this rule in your repository to use the new bypass rule for the `Protect version branches` ruleset that allows maintainers to force-merge.