Update `package:sse` to `4.1.2`(#70)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 16378c5..de98c86 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,4 @@
-## 4.1.2-dev
+## 4.1.2
 
 - Send `fetch` requests instead of `XHR` requests.
 - Add an optional `debugKey` parameter to `SseClient` to include in logging.
diff --git a/pubspec.yaml b/pubspec.yaml
index 3de73be..17955de 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: sse
-version: 4.1.2-dev
+version: 4.1.2
 description: >-
   Provides client and server functionality for setting up bi-directional
   communication through Server Sent Events (SSE) and corresponding POST