[Bugfix] Pin xgrammar to 0.1.11 (vllm-project#13338)

Author: mgoin

requirements-common.txt

@@ -20,7 +20,7 @@ tiktoken >= 0.6.0  # Required for DBRX tokenizer
 lm-format-enforcer >= 0.10.9, < 0.11
 outlines == 0.1.11
 lark == 1.2.2 
-xgrammar >= 0.1.11; platform_machine == "x86_64"
+xgrammar == 0.1.11; platform_machine == "x86_64"
 typing_extensions >= 4.10
 filelock >= 3.16.1 # need to contain https://github.com/tox-dev/filelock/pull/317
 partial-json-parser # used for parsing partial JSON outputs