site: fix different font-size between jsx demo and tsx demo (#48448)

.dumi/theme/common/LiveCode.tsx

@@ -27,7 +27,7 @@ const useStyle = createStyles(({ token, css }) => {
 
         .dumi-default-source-code > pre,
         .dumi-default-source-code-scroll-content > pre {
-          font-size: 13px;
+          font-size: ${token.fontSize}px;
           line-height: 2;
           font-family: 'Lucida Console', Consolas, Monaco, 'Andale Mono', 'Ubuntu Mono', monospace;
         }

components/grid/demo/playground.md

@@ -20,7 +20,7 @@ A simple playground for column count and gutter.
 }
 #components-grid-demo-playground pre {
   padding: 8px 16px;
-  font-size: 13px;
+  font-size: 14px;
   background: #f9f9f9;
   border-radius: 6px;
 }