Bump minimum Swift version to 5.9

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.8
+// swift-tools-version:5.9
 //===----------------------------------------------------------------------===//
 //
 // This source file is part of the SwiftNIO open source project

README.md

@@ -10,7 +10,7 @@ There are a number of reasons to provide a programmatic SSH implementation. One
 
 Another good reason to provide programmatic SSH is that it is not uncommon for services to need to interact with other services in a way that involves running commands. While `Process` solves this for the local use-case, sometimes the commands that need to be invoked are remote. While `Process` could launch an `ssh` client as a sub-process in order to run this invocation, it can be substantially more straightforward to simply invoke SSH directly. This is [`libssh2`](https://www.libssh2.org)'s target use-case. SwiftNIO SSH provides the equivalent of the networking and cryptographic layer of libssh2, allowing motivated users to drive SSH sessions directly from within Swift services.
 
-The most recent versions of SwiftNIO SSH support Swift 5.7 and newer. The minimum Swift version supported by SwiftNIO SSH releases are detailed below:
+The most recent versions of SwiftNIO SSH support Swift 5.9 and newer. The minimum Swift version supported by SwiftNIO SSH releases are detailed below:
 
 SwiftNIO SSH      | Minimum Swift Version
 ------------------|----------------------
@@ -19,7 +19,8 @@ SwiftNIO SSH      | Minimum Swift Version
 `0.4.0 ..< 0.5.0` | 5.4
 `0.5.0 ..< 0.6.2` | 5.5.2
 `0.6.2 ..< 0.9.0` | 5.6
-`0.9.0 ...`       | 5.8
+`0.9.0 ..< 0.9.2` | 5.8
+`0.9.2 ...`       | 5.9
 
 ## What does SwiftNIO SSH support?