Update OS minimum version to Ubuntu 20.04

Author: MikeMcC399

docs/guides/getting-started/installing-cypress.mdx

@@ -155,7 +155,7 @@ Cypress is a desktop application that is installed on your computer. The desktop
 application supports these operating systems:
 
 - **macOS** 10.9 and above _(Intel or Apple Silicon 64-bit (x64 or arm64))_
-- **Linux** Ubuntu 12.04 and above, Fedora 21 and Debian 8 _(x86_64 or Arm
+- **Linux** Ubuntu 20.04 and above, Fedora 21 and Debian 8 _(x86_64 or Arm
   64-bit (x64 or arm64))_ (see [Linux Prerequisites](#Linux-Prerequisites) down
   below)
 - **Windows** 7 and above _(64-bit only)_