test: remove debug console.log left in SlugField overrides fields test suite (#16279)

# Overview

Removes a debug `console.log` left in the `SlugField` test collection's
`overrides` callback that was introduced in #14824

## Key Changes

- Removed `console.log({ field: defaultField.fields[1] })` from the
`readOnlySlug` override
- Cast `defaultField.fields[1]` as `TextField` to fix pre-existing
TypeScript errors on that line

Author: PatrikKozak

test/fields/collections/SlugField/index.ts

@@ -38,8 +38,7 @@ const SlugField: CollectionConfig = {
       checkboxName: 'generateReadOnlySlug',
       required: false,
       overrides: (defaultField) => {
-        console.log({ field: defaultField.fields[1] })
-        defaultField.fields[1].admin.readOnly = true
+        ;(defaultField.fields[1] as TextField).admin!.readOnly = true
 
         return defaultField
       },