[Misc] Add include dir to .gitignore (#1771)

### What this PR does / why we need it?
Add `include` dir to `.gitignore`.

### Does this PR introduce _any_ user-facing change?

### How was this patch tested?


- vLLM version: v0.9.2
- vLLM main:
vllm-project/vllm@66f6fbd

Signed-off-by: shen-shanshan <467638484@qq.com>

Author: shen-shanshan

.gitignore

@@ -198,3 +198,4 @@ kernel_meta/
 /vllm_ascend/_version.py
 # build info file generated by setup.py
 /vllm_ascend/_build_info.py
+/vllm_ascend/include/