Update Learn landing page

- Remove "liquidity and scalability" article
- Add card for agglayer

Author: hsutaiyu

docs/learn/agglayer.md

@@ -1,4 +1,4 @@
-# Aggregation layer
+# Polygon AggLayer
 
 Solving the scalability problem in blockchains means scaling access to shared state and liquidity across multiple chains. To do so requires a new approach to blockchain architecture, namely, aggregated blockchains. Polygon Labs researchers and engineers have designed a solution -- the **aggregation layer**, or **AggLayer** -- which will seamlessly connect any ZK-enabled L2 or L1 chain for near-instant cross-chain transactions, and shared state and liquidity across chains.
 

docs/learn/index.md

@@ -31,9 +31,9 @@ hide:
 </div>
 <div class="grid-container">
    <div class="grid-item">
-      <a href="./liquidity-and-scalability">
+      <a href="./agglayer">
          <div class="product-list-item-header">
-            <div class="feature-card-heading">Liquidity and scalability</div>
+            <div class="feature-card-heading">Polygon AggLayer</div>
          </div>
          <p class="feature-paragraph">ZK-powered L2s to unify liquidity across ecosystem and scale on demand.</p>
       </a>

docs/learn/liquidity-and-scalability.md

@@ -572,7 +572,7 @@ nav:
   - Learn:
       - Learn: learn/index.md
       - Welcome: learn/welcome.md
-      - Unified liquidity and scalability: learn/liquidity-and-scalability.md
+      - Polygon AggLayer: learn/agglayer.md
       - Polygon protocols: learn/polygon-protocols.md
       - Polygon 2.0 architecture: learn/deep-dive-arch.md