Diff code blocks have different padding from normal code blocks

[szokeasaurusrex]

Steps to Reproduce

1. Create a normal code block on a docs page, for example:

```python
def hello_world():
    print("hello_world")

hello_world()
print("done")
```

2. Create a diff code block on a docs page, for example:

```python diff
def hello_world():
-     print("hello_world")
+     print("Hello, world!")

hello_world()
- print("done")
+ print("Done!")
 ```

Expected Result

Both code blocks have the same padding

Actual Result

The blocks have different padding. This example, which is the rendered preview of #10508, demonstrates the problem.

Additional Info

No response

[a-hariti]

I believe the ideal should be one extra column on the left (a space or +/-) with the same padding as normal code

wyt @szokeasaurusrex?

[a-hariti]

this code block:

 def hello_world():
+    print("hello_world")
-    print("Hello, world!")

produces: which is inline with a non diff code block

normal code blocks