[Fix] fix type issue of env flag value MODELOPT_MAX_TOKENS_PER_EXPERT (#11709)

Signed-off-by: zejunchen-zejun <zejun.chen@amd.com>

sgl-kernel/python/sgl_kernel/gemm.py

@@ -465,7 +465,7 @@ def scaled_fp4_experts_quant(
     # larger models.
     import os
 
-    MAX_TOKENS_PER_EXPERT = os.environ.get("MODELOPT_MAX_TOKENS_PER_EXPERT", 65536)
+    MAX_TOKENS_PER_EXPERT = int(os.environ.get("MODELOPT_MAX_TOKENS_PER_EXPERT", 65536))
     assert m_numtopk <= MAX_TOKENS_PER_EXPERT * topk, (
         f"m_numtopk must be less than MAX_TOKENS_PER_EXPERT("
         f"{MAX_TOKENS_PER_EXPERT})"