chore: update TC AITech unit (#11100)

<!--
Before opening a pull request, please read the [contributing
guidelines](https://github.com/pancakeswap/pancake-frontend/blob/develop/CONTRIBUTING.md)
first
-->


<!-- start pr-codex -->

---

## PR-Codex overview
This PR updates the `TradingCompetition` component to modify the reward
unit from dollars (`$`) to `AITECH`, reflecting a change in the type of
reward for the trading competition.

### Detailed summary
- Changed the `unit` value from `'$'` to `'AITECH'` in the reward
configuration.
- Updated the URL for the trading competition article to ensure it
points to the correct resource.

> ✨ Ask PR-Codex anything about this PR by commenting with `/codex {your
question}`

<!-- end pr-codex -->

apps/web/src/components/PhishingWarningBanner/TradingCompetition.tsx

@@ -10,7 +10,7 @@ export const tradingCompetitionConfig = {
     learnMoreUrl:
       'https://blog.pancakeswap.finance/articles/pancake-swap-x-solidus-ai-tech-trading-competition-50-000-in-rewards?utm_source=Website&utm_medium=infostripe&utm_campaign=AITECH&utm_id=TradingCompetition',
     reward: '50,000',
-    unit: '$',
+    unit: 'AITECH',
   },
   bfg: {
     imgUrl: 'bfg_competition',