Update docs

Author: gmazoyer

docs/docs/reference/infrahub-cli/infrahub-upgrade.mdx

@@ -15,6 +15,7 @@ $ infrahub upgrade [OPTIONS] [CONFIG_FILE]
 **Options**:
 
 * `--check / --no-check`: Check the state of the system without upgrading.  [default: no-check]
+* `--rebase-branches / --no-rebase-branches`: Rebase and apply migrations to branches if required.  [default: no-rebase-branches]
 * `--install-completion`: Install completion for the current shell.
 * `--show-completion`: Show completion for the current shell, to copy it or customize the installation.
 * `--help`: Show this message and exit.