docs: fix typo in container.ts comment ("a the" -> "the") (#18223)

## Description
Fixed a typo in the container.ts comment where "a the" was incorrectly
written as "the" for better readability.

## Test Plan
- [x] Verified the change is purely documentation-related and doesn't
affect functionality
- [x] Ensured the comment is more readable and grammatically correct
- [x] No tests needed as this is a documentation-only change

## Changes
- Modified comment in `packages/tailwindcss/src/compat/container.ts`
- Changed "When setting a the `screens` in v3" to "When setting the
`screens` in v3"

Co-authored-by: 中野 博文 <hirofumi0082@gmail.com>
Co-authored-by: Jordan Pittman <jordan@cryptica.me>

packages/tailwindcss/src/compat/container.ts

@@ -50,7 +50,7 @@ export function buildCustomContainerUtilityRules(
   if (typeof screens === 'object' && screens !== null) {
     breakpointOverwrites = new Map()
 
-    // When setting a the `screens` in v3, you were overwriting the default
+    // When setting the `screens` in v3, you were overwriting the default
     // screens config. To do this in v4, you have to manually unset all core
     // screens.