typo: solid start index.mdx (#742)

Author: amanuay

src/routes/solid-start/index.mdx

@@ -24,7 +24,7 @@ A driving principle of SolidStart is that code should be _isomorphic_ — th
 
 SolidStart features the following capabilities:
 
-- **Fine-grained reactivity** — Powered by SolidJS and it's fine-grained reactivity.
+- **Fine-grained reactivity** — Powered by SolidJS and its fine-grained reactivity.
 - **Isomorphic, nested routing** — The same routes are rendered regardless of whether the page is on the client or server.
   Route nesting provides parent-child relationships that simplify application logic.
 - **Multiple rendering modes** — Can be used to create CSR, SSR (Sync, Async and Streaming), and SSG applications.