[docs] Mark ubuntu-20.04 as deprecated (#11641)

Author: shamil-mubarakshin

README.md

@@ -22,7 +22,7 @@ To build a VM machine from this repo's source, see the [instructions](docs/creat
 | --------------------|---------------------|--------------------|--------------------|
 | Ubuntu 24.04 | `ubuntu-latest` or `ubuntu-24.04` | [ubuntu-24.04] | ![Endpoint Badge](https://img.shields.io/endpoint?url=https%3A%2F%2Fgist.githubusercontent.com%2Fsubir0071%2F385e39188f4280878bada99250e99db7%2Fraw%2Fubuntu24.json) |
 | Ubuntu 22.04 | `ubuntu-22.04` | [ubuntu-22.04] | ![Endpoint Badge](https://img.shields.io/endpoint?url=https%3A%2F%2Fgist.githubusercontent.com%2Fsubir0071%2F385e39188f4280878bada99250e99db7%2Fraw%2Fubuntu22.json) |
-| Ubuntu 20.04 | `ubuntu-20.04` | [ubuntu-20.04] | ![Endpoint Badge](https://img.shields.io/endpoint?url=https%3A%2F%2Fgist.githubusercontent.com%2Fsubir0071%2F385e39188f4280878bada99250e99db7%2Fraw%2Fubuntu20.json) |
+| Ubuntu 20.04 <sup>deprecated</sup> | `ubuntu-20.04` | [ubuntu-20.04] | ![Endpoint Badge](https://img.shields.io/endpoint?url=https%3A%2F%2Fgist.githubusercontent.com%2Fsubir0071%2F385e39188f4280878bada99250e99db7%2Fraw%2Fubuntu20.json) |
 | macOS 15 <sup>beta</sup> | `macos-15-large`| [macOS-15] | ![Endpoint Badge](https://img.shields.io/endpoint?url=https%3A%2F%2Fgist.githubusercontent.com%2Fsubir0071%2F385e39188f4280878bada99250e99db7%2Fraw%2Fmacos-15.json) |
 | macOS 15 Arm64 <sup>beta</sup> | `macos-15` or `macos-15-xlarge` | [macOS-15-arm64] | ![Endpoint Badge](https://img.shields.io/endpoint?url=https%3A%2F%2Fgist.githubusercontent.com%2Fsubir0071%2F385e39188f4280878bada99250e99db7%2Fraw%2Fmacos-15-arm64.json) |
 | macOS 14 | `macos-latest-large` or `macos-14-large`| [macOS-14] | ![Endpoint Badge](https://img.shields.io/endpoint?url=https%3A%2F%2Fgist.githubusercontent.com%2Fsubir0071%2F385e39188f4280878bada99250e99db7%2Fraw%2Fmacos-14.json) |