Fix figures in design doc (#18612)

Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>

docs/design/kernel/paged_attention.md

@@ -142,8 +142,6 @@ title: vLLM Paged Attention
 
 <figure markdown="span">
   ![](../../assets/kernel/query.png){ align="center" alt="query" width="70%" }
-    <figcaption>
-</figcaption>
 </figure>
 
 - Each thread defines its own `q_ptr` which points to the assigned
@@ -153,8 +151,6 @@ title: vLLM Paged Attention
 
 <figure markdown="span">
   ![](../../assets/kernel/q_vecs.png){ align="center" alt="q_vecs" width="70%" }
-    <figcaption>
-</figcaption>
 </figure>
 
   ```cpp
@@ -194,8 +190,6 @@ title: vLLM Paged Attention
 
 <figure markdown="span">
   ![](../../assets/kernel/key.png){ align="center" alt="key" width="70%" }
-    <figcaption>
-</figcaption>
 </figure>
 
 - The diagram above illustrates the memory layout for key data. It
@@ -211,8 +205,6 @@ title: vLLM Paged Attention
 
 <figure markdown="span">
   ![](../../assets/kernel/k_vecs.png){ align="center" alt="k_vecs" width="70%" }
-    <figcaption>
-</figcaption>
 </figure>
 
   ```cpp
@@ -372,20 +364,14 @@ title: vLLM Paged Attention
 
 <figure markdown="span">
   ![](../../assets/kernel/value.png){ align="center" alt="value" width="70%" }
-  <figcaption>
-</figcaption>
 </figure>
 
 <figure markdown="span">
   ![](../../assets/kernel/logits_vec.png){ align="center" alt="logits_vec" width="50%" }
-  <figcaption>
-</figcaption>
 </figure>
 
 <figure markdown="span">
   ![](../../assets/kernel/v_vec.png){ align="center" alt="v_vec" width="70%" }
-  <figcaption>
-</figcaption>
 </figure>
 
 - Now we need to retrieve the value data and perform dot multiplication