[doc] fix supported_models (#6930)

### What this PR does / why we need it?

Add Experimental supported model/feature for supported_models.md

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

### How was this patch tested?

- vLLM version: v0.16.0
- vLLM main:
15d76f74e2

Signed-off-by: zzzzwwjj <1183291235@qq.com>

docs/source/user_guide/support_matrix/supported_models.md

@@ -5,8 +5,9 @@ Get the latest info here: <https://github.com/vllm-project/vllm-ascend/issues/16
 **Legend Description**:
 
 - ✅ = Supported model/feature
-- ❌  = Not supported model/feature
-- 🟡  = Not tested or verified
+- 🔵 = Experimental supported model/feature
+- ❌ = Not supported model/feature
+- 🟡 = Not tested or verified
 
 ## Text-Only Language Models