[SPARK-25262][DOC][FOLLOWUP] Fix link tags in html table

## What changes were proposed in this pull request?

Markdown links are not working inside html table. We should use html link tag.

## How was this patch tested?

Verified in IntelliJ IDEA's markdown editor and online markdown editor.

Closes apache#22588 from viirya/SPARK-25262-followup.

Authored-by: Liang-Chi Hsieh <[email protected]>
Signed-off-by: hyukjinkwon <[email protected]>

Author: viirya

docs/running-on-kubernetes.md

@@ -680,15 +680,15 @@ specific to Spark on Kubernetes.
   <td><code>spark.kubernetes.driver.limit.cores</code></td>
   <td>(none)</td>
   <td>
-    Specify a hard cpu [limit](https://kubernetes.io/docs/concepts/configuration/manage-compute-resources-container/#resource-requests-and-limits-of-pod-and-container) for the driver pod.
+    Specify a hard cpu <a href="https://kubernetes.io/docs/concepts/configuration/manage-compute-resources-container/#resource-requests-and-limits-of-pod-and-container">limit</a> for the driver pod.
   </td>
 </tr>
 <tr>
   <td><code>spark.kubernetes.executor.request.cores</code></td>
   <td>(none)</td>
   <td>
-    Specify the cpu request for each executor pod. Values conform to the Kubernetes [convention](https://kubernetes.io/docs/concepts/configuration/manage-compute-resources-container/#meaning-of-cpu). 
-    Example values include 0.1, 500m, 1.5, 5, etc., with the definition of cpu units documented in [CPU units](https://kubernetes.io/docs/tasks/configure-pod-container/assign-cpu-resource/#cpu-units).   
+    Specify the cpu request for each executor pod. Values conform to the Kubernetes <a href="https://kubernetes.io/docs/concepts/configuration/manage-compute-resources-container/#meaning-of-cpu">convention</a>.
+    Example values include 0.1, 500m, 1.5, 5, etc., with the definition of cpu units documented in <a href="https://kubernetes.io/docs/tasks/configure-pod-container/assign-cpu-resource/#cpu-units">CPU units</a>.
     This is distinct from <code>spark.executor.cores</code>: it is only used and takes precedence over <code>spark.executor.cores</code> for specifying the executor pod cpu request if set. Task 
     parallelism, e.g., number of tasks an executor can run concurrently is not affected by this.
   </td>
@@ -697,7 +697,7 @@ specific to Spark on Kubernetes.
   <td><code>spark.kubernetes.executor.limit.cores</code></td>
   <td>(none)</td>
   <td>
-    Specify a hard cpu [limit](https://kubernetes.io/docs/concepts/configuration/manage-compute-resources-container/#resource-requests-and-limits-of-pod-and-container) for each executor pod launched for the Spark Application.
+    Specify a hard cpu <a href="https://kubernetes.io/docs/concepts/configuration/manage-compute-resources-container/#resource-requests-and-limits-of-pod-and-container">limit</a> for each executor pod launched for the Spark Application.
   </td>
 </tr>
 <tr>