Update the links for Package bot and drop Ubuntu 16.04

Author: shahmishal

README.md

@@ -6,8 +6,7 @@
 | | **Architecture** | **main** | **Package** |
 |---|:---:|:---:|:---:|
 | **macOS**        | x86_64 |[![Build Status](https://ci.swift.org/job/oss-swift-incremental-RA-macos/lastCompletedBuild/badge/icon)](https://ci.swift.org/job/oss-swift-incremental-RA-macos)|[![Build Status](https://ci.swift.org/job/oss-swift-package-macos/lastCompletedBuild/badge/icon)](https://ci.swift.org/job/oss-swift-package-macos)|
-| **Ubuntu 16.04** | x86_64 | [![Build Status](https://ci.swift.org/job/oss-swift-incremental-RA-linux-ubuntu-16_04/lastCompletedBuild/badge/icon)](https://ci.swift.org/job/oss-swift-incremental-RA-linux-ubuntu-16_04)|[![Build Status](https://ci.swift.org/job/oss-swift-package-linux-ubuntu-16_04/lastCompletedBuild/badge/icon)](https://ci.swift.org/job/oss-swift-package-linux-ubuntu-16_04)|
-| **Ubuntu 18.04** | x86_64 | [![Build Status](https://ci.swift.org/job/oss-swift-incremental-RA-linux-ubuntu-18_04/lastCompletedBuild/badge/icon)](https://ci.swift.org/job/oss-swift-incremental-RA-linux-ubuntu-18_04)|[![Build Status](https://ci.swift.org/job/oss-swift-package-linux-ubuntu-18_04/lastCompletedBuild/badge/icon)](https://ci.swift.org/job/oss-swift-package-linux-ubuntu-18_04)|
+| **Ubuntu 18.04** | x86_64 | [![Build Status](https://ci.swift.org/job/oss-swift-package-ubuntu-18_04/lastCompletedBuild/badge/icon)](https://ci.swift.org/job/oss-swift-package-ubuntu-18_04)|[![Build Status](https://ci.swift.org/job/oss-swift-package-ubuntu-18_04/lastCompletedBuild/badge/icon)](https://ci.swift.org/job/oss-swift-package-ubuntu-18_04)|
 | **Ubuntu 20.04** | x86_64 | [![Build Status](https://ci.swift.org/job/oss-swift-package-ubuntu-20_04/lastCompletedBuild/badge/icon)](https://ci.swift.org/job/oss-swift-package-ubuntu-20_04)|[![Build Status](https://ci.swift.org/job/oss-swift-package-ubuntu-20_04/lastCompletedBuild/badge/icon)](https://ci.swift.org/job/oss-swift-package-ubuntu-20_04)|
 | **CentOS 8** | x86_64 | [![Build Status](https://ci.swift.org/job/oss-swift-package-centos-8/lastCompletedBuild/badge/icon)](https://ci.swift.org/job/oss-swift-package-centos-8)|[![Build Status](https://ci.swift.org/job/oss-swift-package-centos-8/lastCompletedBuild/badge/icon)](https://ci.swift.org/job/oss-swift-package-centos-8)|
 | **CentOS 7** | x86_64 | [![Build Status](https://ci.swift.org/job/oss-swift-package-centos-7/lastCompletedBuild/badge/icon)](https://ci.swift.org/job/oss-swift-package-centos-7)|[![Build Status](https://ci.swift.org/job/oss-swift-package-centos-7/lastCompletedBuild/badge/icon)](https://ci.swift.org/job/oss-swift-package-centos-7)|