### What this PR does / why we need it?
The current implementation will result in duplicate generation of
`sin_cos_cache` in rope when `kv_seqlen` > 4k, because the
initialization length of the `sin_cos_cache` is only 4k.
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
After this PR merged, sin_cos_cache will not increase in forward func,
so `test_native_rope_deepseek_forward_cache_handling` is not necessary.
- vLLM version: v0.10.1.1
- vLLM main:
60f0843ef8
Signed-off-by: zzzzwwjj <1183291235@qq.com>
4df8df5b94