Fix Swift Package Manager error.

[thorikawa]

• Use Task.capture instead of SwiftCLI.capture to solve SiftCLI issue.

  $ swift run maskrcnn download example
  /Users/poly/ws/Mask-RCNN-CoreML/Sources/maskrcnn/Docker.swift:8:34: error: 'capture(_:arguments:directory:)' has been renamed to 'Task.capture'
          let _ = try SwiftCLI.capture("docker",
                               ^~~~~~~
                               Task.capture
  SwiftCLI.capture:2:13: note: 'capture(_:arguments:directory:)' has been explicitly marked unavailable here
  public func capture(_ executable: String, arguments: [String], directory: String? = nil) throws -> SwiftCLI.CaptureResult
          ^
  /Users/poly/ws/Mask-RCNN-CoreML/Sources/maskrcnn/Docker.swift:48:35: error: 'capture(_:arguments:directory:)' has been renamed to 'Task.capture'
      let result = try SwiftCLI.capture("docker", arguments:allArguments)
                                ^~~~~~~
                                Task.capture
  SwiftCLI.capture:2:13: note: 'capture(_:arguments:directory:)' has been explicitly marked unavailable here
  public func capture(_ executable: String, arguments: [String], directory: String? = nil) throws -> SwiftCLI.CaptureResult
          ^

• Update dependencies to solve manifest parse error.

  $ swift run maskrcnn download example
  Fetching https://github.com/jakeheis/SwiftCLI
  Fetching https://github.com/Alamofire/Alamofire.git
  Fetching https://github.com/apple/swift-protobuf.git
  https://github.com/Alamofire/Alamofire.git @ 4.8.0: error: manifest parse error(s):
  /var/folders/yl/hzrq7fjd3j96yfsqwzlmcgmm0000gr/T/TemporaryFile.2P2hUs.swift:40:29: error: cannot convert value of type 'Int' to expected element type 'SwiftVersion'
  swiftLanguageVersions: [3, 4]