chore: Bump event source to 3.1.1 (#234)

This doesn't actually change any behavior because we override the
default retry behavior, and that is all that changed since 3.1.0.
However, we do not want the SDK to drift too far from the eventsource
implementation, so I try to update it each time.

LaunchDarkly.podspec

@@ -35,6 +35,6 @@ Pod::Spec.new do |ld|
   ld.swift_version = '5.0'
 
   ld.subspec 'Core' do |es|
-    es.dependency 'LDSwiftEventSource', '3.1.0'
+    es.dependency 'LDSwiftEventSource', '3.1.1'
   end
 end

LaunchDarkly.xcodeproj/project.pbxproj

@@ -1882,7 +1882,7 @@
 			repositoryURL = "https://github.com/LaunchDarkly/swift-eventsource.git";
 			requirement = {
 				kind = exactVersion;
-				version = 3.1.0;
+				version = 3.1.1;
 			};
 		};
 		B4903D9624BD61B200F087C4 /* XCRemoteSwiftPackageReference "OHHTTPStubs" */ = {

Package.swift

@@ -19,7 +19,7 @@ let package = Package(
         .package(url: "https://github.com/AliSoftware/OHHTTPStubs.git", .exact("9.1.0")),
         .package(url: "https://github.com/Quick/Quick.git", .exact("4.0.0")),
         .package(url: "https://github.com/Quick/Nimble.git", .exact("9.2.1")),
-        .package(name: "LDSwiftEventSource", url: "https://github.com/LaunchDarkly/swift-eventsource.git", .exact("3.1.0"))
+        .package(name: "LDSwiftEventSource", url: "https://github.com/LaunchDarkly/swift-eventsource.git", .exact("3.1.1"))
     ],
     targets: [
         .target(