Bump swift-format to 5.9 (#20)

Bump swift-format to 5.9

### Motivation

As per apple/swift-openapi-generator#175.

### Modifications

Bump swift-format, update to make soundness pass.

### Result

Using swift-format 5.9.

### Test Plan

Soundness passed.


Reviewed by: dnadoba

Builds:
     ✔︎ pull request validation (5.10) - Build finished. 
     ✔︎ pull request validation (5.8) - Build finished. 
     ✔︎ pull request validation (5.9) - Build finished. 
     ✔︎ pull request validation (nightly) - Build finished. 
     ✔︎ pull request validation (soundness) - Build finished. 

#20

Tests/OpenAPIAsyncHTTPClientTests/Test_AsyncHTTPClientTransport.swift

@@ -118,8 +118,8 @@ class Test_AsyncHTTPClientTransport: XCTestCase {
 
 struct TestSender: HTTPRequestSending {
     var sendClosure:
-        @Sendable (AsyncHTTPClientTransport.Request, HTTPClient, TimeAmount) async throws -> AsyncHTTPClientTransport
-            .Response
+        @Sendable (AsyncHTTPClientTransport.Request, HTTPClient, TimeAmount) async throws ->
+            AsyncHTTPClientTransport.Response
     func send(
         request: AsyncHTTPClientTransport.Request,
         with client: HTTPClient,

docker/Dockerfile

@@ -17,7 +17,7 @@ RUN mkdir -p $HOME/.tools
 RUN echo 'export PATH="$HOME/.tools:$PATH"' >> $HOME/.profile
 
 # swift-format
-ARG swiftformat_version=508.0.0
+ARG swiftformat_version=509.0.0
 RUN git clone --branch $swiftformat_version --depth 1 https://github.com/apple/swift-format $HOME/.tools/swift-format-source
 RUN cd $HOME/.tools/swift-format-source && swift build -c release
-RUN ln -s $HOME/.tools/swift-format-source/.build/release/swift-format $HOME/.tools/swift-format
+RUN ln -s $HOME/.tools/swift-format-source/.build/release/swift-format $HOME/.tools/swift-format