[SPARK-46464][DOC] Fix the scroll issue of tables when overflow

### What changes were proposed in this pull request?

https://spark.apache.org/docs/3.4.1/running-on-kubernetes.html#spark-properties
https://spark.apache.org/docs/latest/running-on-kubernetes.html#spark-properties

As listed above, the doc content in 3.5.0 cannot scroll horizontally. Users can only see the rest of its content when a table overflows if they zoom out as much as possible, resulting in hard-to-read minor characters.

This PR changes the HTML body overflow-x from hidden to auto to enable the underlying table to scroll horizontally.

### Why are the changes needed?

Fix documentation

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

no

### How was this patch tested?

#### Before
![image](https://github.com/apache/spark/assets/8326978/437bee91-ab0d-4616-aaaf-f99171dcf9f9)

#### After
![image](https://github.com/apache/spark/assets/8326978/327ed82b-3e14-4a27-be1a-835a7b21c000)

### Was this patch authored or co-authored using generative AI tooling?

no

Closes #44423 from yaooqinn/SPARK-46464.

Authored-by: Kent Yao <yao@apache.org>
Signed-off-by: Kent Yao <yao@apache.org>

docs/css/custom.css

@@ -7,7 +7,7 @@ body {
   font-style: normal;
   font-weight: 400;
   overflow-wrap: anywhere;
-  overflow-x: hidden;
+  overflow-x: auto;
   padding-top: 80px;
   padding-bottom: 20px;
 }