docs: link runtime prerequisites instead of restating versions (#2518)

The getting-started prerequisites listed 'Node.js 20+', but the Node SDK requires '^20.19.0 || >=22.12.0', so 20.0-20.18 and all of 21.x fail to install. nodejs/README.md already states the real constraint.

Point each language at the Prerequisites section of its own README, matching how docs/setup/bundled-cli.md now refers to them, so there is one place per SDK to keep current.

Co-authored-by: Zhangyi Yuan <j-zhangyiyuan@microsoft.com>

Author: rinceyuan

docs/getting-started.md

@@ -19,8 +19,7 @@ Copilot: In Tokyo it's 75°F and sunny. Great day to be outside!
 Before you begin, make sure you have:
 
 * **GitHub Copilot CLI** installed and authenticated (the Node.js, Python, and .NET SDKs provide the CLI automatically—see [Bundled CLI](./setup/bundled-cli.md). Required for Go, Java, and Rust unless using their application-level CLI bundling features.)
-* Your preferred language runtime:
-  * **Node.js** 20+ or **Python** 3.11+ or **Go** 1.24+ or **Rust** 1.94+ or **Java** 17+ or **.NET** 8.0+
+* Your preferred language runtime, at or above the version its SDK requires. Each SDK states its own floor in the Prerequisites section of its README: [Node.js](../nodejs/README.md#prerequisites), [Python](../python/README.md#prerequisites), [Go](../go/README.md#prerequisites), [Rust](../rust/README.md#prerequisites), [Java](../java/README.md#prerequisites), [.NET](../dotnet/README.md#prerequisites).
 
 Verify the CLI is working: