Remove the docc plugin dependency from main (to make a docs branch) (apple#99)

Author: phausler

Package.swift

@@ -17,9 +17,7 @@ let package = Package(
     .library(name: "AsyncSequenceValidation", targets: ["AsyncSequenceValidation"]),
     .library(name: "_CAsyncSequenceValidationSupport", type: .static, targets: ["AsyncSequenceValidation"])
   ],
-  dependencies: [
-    .package(url: "https://github.com/apple/swift-docc-plugin", from: "1.0.0"),
-  ],
+  dependencies: [],
   targets: [
     .target(
       name: "AsyncAlgorithms"),