Remove mention of CentOS from the README.md since it is not particular relevant anymore

Author: cmcgee1024

README.md

@@ -44,7 +44,6 @@ Target: x86_64-unknown-linux-gnu
 ## Platform support
 
 - Linux-based platforms listed on https://swift.org/download
-  - CentOS 7 will not be supported due to some dependencies of swiftly not supporting it, however.
 
 Right now, swiftly is in early stages of development and is supported on Linux and macOS. For more detailed information about swiftly's intended features and implementation, check out the [design document](DESIGN.md).