[cxx-interop] Remove -experimental-c-foreign-reference-types flag

The flag is being removed in the compiler: swiftlang/swift#82680.

C foreign reference types will now be available unconditionally.

rdar://150308819

Author: egorzhdan

Sources/SwiftOptions/Options.swift

@@ -532,7 +532,6 @@ extension Option {
   public static let experimentalAllowModuleWithCompilerErrors: Option = Option("-experimental-allow-module-with-compiler-errors", .flag, attributes: [.helpHidden, .frontend, .noDriver], helpText: "Attempt to output .swiftmodule, regardless of compilation errors")
   public static let experimentalAllowNonResilientAccess: Option = Option("-experimental-allow-non-resilient-access", .flag, attributes: [.frontend], helpText: "Deprecated; use -allow-non-resilient-access instead")
   public static let experimentalAllowedReexportedModules: Option = Option("-experimental-allowed-reexported-modules=", .commaJoined, attributes: [.noDriver], helpText: "Allow reexporting symbols from the provided modules if they are themselves exported from the main module. This is a comma separated list of module names.")
-  public static let experimentalCForeignReferenceTypes: Option = Option("-experimental-c-foreign-reference-types", .flag, attributes: [.helpHidden, .frontend, .moduleInterface], helpText: "Enable experimental C foreign references types (with reference counting).")
   public static let experimentalClangImporterDirectCc1Scan: Option = Option("-experimental-clang-importer-direct-cc1-scan", .flag, attributes: [.helpHidden, .frontend], helpText: "Enables swift driver to construct swift-frontend invocations using -direct-clang-cc1-module-build")
   public static let emitModuleSeparately: Option = Option("-experimental-emit-module-separately", .flag, attributes: [.helpHidden], helpText: "Emit module files as a distinct job")
   public static let experimentalEmitVariantModule: Option = Option("-experimental-emit-variant-module", .flag, attributes: [], helpText: "When a target variant triple is specified, the same driver invocation will emit two Swift modules, one for the primary target and one for the variant.")