Fix some more merge bugs.

Add back Xcode 12 CI!
Update ReactiveSwift version to 6.4.0 (for Xcode 12).

Author: mluisbrown

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
         xcode:
           - 11.4
           - 11.7
-          # - 12.0
+          - 12.0
     steps:
       - uses: actions/checkout@v2
       - name: Select Xcode ${{ matrix.xcode }}

Examples/CaseStudies/SwiftUICaseStudies/04-HigherOrderReducers-Recursion.swift

@@ -1,4 +1,5 @@
 import ComposableArchitecture
+import ReactiveSwift
 import SwiftUI
 
 private let readMe = """
@@ -69,7 +70,7 @@ let nestedReducer = Reducer<
 
     state.description = name
     return Effect(value: .exclaim)
-      .debounce(id: ExclaimId(), for: 1, scheduler: DispatchQueue.main)
+      .debounce(id: ExclaimId(), interval: 1, scheduler: QueueScheduler.main)
   }
 }
 

Examples/TicTacToe/Tests/LoginCoreTests.swift

@@ -75,7 +75,7 @@ class LoginCoreTests: XCTestCase {
             Effect(value: .init(token: "deadbeefdeadbeef", twoFactorRequired: false))
           }
         ),
-        mainQueue: AnyScheduler(self.scheduler)
+        mainQueue: self.scheduler
       )
     )
 

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.1
+// swift-tools-version:5.2
 
 import PackageDescription
 
@@ -26,7 +26,7 @@ let package = Package(
   ],
   dependencies: [
     .package(url: "https://github.com/pointfreeco/swift-case-paths", from: "0.1.1"),
-    .package(url: "https://github.com/ReactiveCocoa/ReactiveSwift", from: "6.3.0"),
+    .package(url: "https://github.com/ReactiveCocoa/ReactiveSwift", from: "6.4.0"),
   ],
   targets: [
     .target(