Update Prerequisites

Update Prerequisites for install.md as per metrics on [latest node release notes](https://github.com/input-output-hk/cardano-node/releases/tag/8.1.2)

Author: rdlrt

docs/getting-started/install.md

@@ -9,7 +9,7 @@ To set up your platform, you will need:
 
 | Network | CPU Cores | Free RAM | Free storage | OS for Pasive Node | OS for Stake pool |
 | :---: | :---: | :---: | :---: | :---: | :---: |
-| Mainnet | 2 | 16GB | 75GB of free storage (100GB recommended for future growth | Linux / Windows** / MacOS | Linux |
+| Mainnet | 2 | 24GB | 150GB of free storage (250GB recommended for future growth) | Linux / Windows** / MacOS | Linux |
 | Testnet | 2 | 4GB | 20GB | Linux / Windows** / MacOS | Linux |
 
 ****Note** If you are building on Windows, we recommend using WSL2 under Windows 10 as this provides a development and execution environment that is very similar to Ubuntu.