[Misc] Update deprecation message for --enable-reasoning (vllm-project#18404)

Author: Zerohertz

vllm/engine/arg_utils.py

@@ -577,7 +577,7 @@ def add_cli_args(parser: FlexibleArgumentParser) -> FlexibleArgumentParser:
             action=argparse.BooleanOptionalAction,
             deprecated=True,
             help="[DEPRECATED] The `--enable-reasoning` flag is deprecated as "
-            "of v0.8.6. Use `--reasoning-parser` to specify the reasoning "
+            "of v0.9.0. Use `--reasoning-parser` to specify the reasoning "
             "parser backend instead. This flag (`--enable-reasoning`) will be "
             "removed in v0.10.0. When `--reasoning-parser` is specified, "
             "reasoning mode is automatically enabled.")