Update the README to include the Raspberry Pi name in community-hosted CI

Author: shahmishal

README.md

@@ -14,7 +14,7 @@
 
 | **OS** | **Architecture** | **Build** |
 |---|:---:|:---:|
-|**[Debian 9.1](https://github.com/apple/swift-community-hosted-continuous-integration/blob/master/nodes/armv7_debian_stretch.json)** | ARMv7 (Raspberry Pi) | [![Build Status](https://ci-external.swift.org/job/oss-swift-RA-linux-debian-9_1/lastCompletedBuild/badge/icon)](https://ci-external.swift.org/job/oss-swift-RA-linux-debian-9_1)|
+|**[Debian 9.1 (Raspberry Pi)](https://github.com/apple/swift-community-hosted-continuous-integration/blob/master/nodes/armv7_debian_stretch.json)** | ARMv7 | [![Build Status](https://ci-external.swift.org/job/oss-swift-RA-linux-debian-9_1/lastCompletedBuild/badge/icon)](https://ci-external.swift.org/job/oss-swift-RA-linux-debian-9_1)|
 |**[Fedora 27](https://github.com/apple/swift-community-hosted-continuous-integration/blob/master/nodes/x86_64_fedora_27.json)** | x86_64 |[![Build Status](https://ci-external.swift.org/job/oss-swift-RA-linux-fedora-27/lastCompletedBuild/badge/icon)](https://ci-external.swift.org/job/oss-swift-RA-linux-fedora-27)|
 |**[Ubuntu 16.04](https://github.com/apple/swift-community-hosted-continuous-integration/blob/master/nodes/x86_64_ubuntu_16_04.json)** | x86_64 |[![Build Status](https://ci-external.swift.org/job/oss-swift-RA-linux-ubuntu-16.04/lastCompletedBuild/badge/icon)](https://ci-external.swift.org/job/oss-swift-RA-linux-ubuntu-16.04)|
 |**[Ubuntu 16.04 (TensorFlow)](https://github.com/apple/swift-community-hosted-continuous-integration/blob/master/nodes/x86_64_ubuntu_16_04_tensorflow.json)** | x86_64 |[![Build Status](https://ci-external.swift.org/job/oss-swift-RA-linux-ubuntu-16.04-tensorflow/lastCompletedBuild/badge/icon)](https://ci-external.swift.org/job/oss-swift-RA-linux-ubuntu-16.04-tensorflow)|