Update packages/bigframes/release-procedure.md

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: shuoweil

packages/bigframes/release-procedure.md

@@ -30,7 +30,7 @@
 
 *   Check image updates:
 
-        legacylibrarian update-image -push
+        legacylibrarian update-image --push
 
 *   Create release PR: