generator: Use Swift 6.0.3 by default (#169)

Author: euanh

Sources/GeneratorCLI/GeneratorCLI.swift

@@ -98,7 +98,7 @@ extension GeneratorCLI {
     var swiftBranch: String? = nil
 
     @Option(help: "Version of Swift to supply in the bundle.")
-    var swiftVersion = "6.0.2-RELEASE"
+    var swiftVersion = "6.0.3-RELEASE"
 
     @Option(
       help: """

Tests/SwiftSDKGeneratorTests/EndToEndTests.swift

@@ -363,7 +363,7 @@ final class Swift510_UbuntuEndToEndTests: XCTestCase {
 
 final class Swift60_UbuntuEndToEndTests: XCTestCase {
   let config = SDKConfiguration(
-    swiftVersion: "6.0.2",
+    swiftVersion: "6.0.3",
     linuxDistributionName: "ubuntu",
     architecture: "aarch64",
     withDocker: false
@@ -430,7 +430,7 @@ final class Swift510_RHELEndToEndTests: XCTestCase {
 
 final class Swift60_RHELEndToEndTests: XCTestCase {
   let config = SDKConfiguration(
-    swiftVersion: "6.0.2",
+    swiftVersion: "6.0.3",
     linuxDistributionName: "rhel",
     architecture: "aarch64",
     withDocker: true  // RHEL-based SDKs can only be built from containers