[BugFix] Fix false assertion with spec-decode=[2,4,..] and TP>2 (#29036)

Signed-off-by: Lucas Wilkinson <lwilkins@redhat.com>
(cherry picked from commit 8f4f77a7)

vllm/config/compilation.py

@@ -917,7 +917,7 @@ class CompilationConfig:
         self, uniform_decode_query_len: int, tensor_parallel_size: int
     ):
         multiple_of = uniform_decode_query_len
-        if tensor_parallel_size > 1:
+        if tensor_parallel_size > 1 and self.pass_config.enable_sequence_parallelism:
             multiple_of = max(uniform_decode_query_len, tensor_parallel_size)
             if (
                 multiple_of % uniform_decode_query_len != 0