stable null safety release (#526)

CHANGELOG.md

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 06e88c2..7707e74 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 0.13.0
+
+* Stable null safety release.
+
 ## 0.13.0-nullsafety.0
 
 * Migrate to null safety.

pubspec.yaml

diff --git a/pubspec.yaml b/pubspec.yaml
index bf9f9a3..9f9512b 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: http
-version: 0.13.0-nullsafety.0
+version: 0.13.0
 homepage: https://github.com/dart-lang/http
 description: A composable, multi-platform, Future-based API for HTTP requests.
 
@@ -7,15 +7,11 @@
   sdk: '>=2.12.0-0 <3.0.0'
 
 dependencies:
-  http_parser: ^4.0.0-nullsafety
-  meta: ^1.3.0-nullsafety.3
-  path: ^1.8.0-nullsafety.1
-  pedantic: ^1.10.0-nullsafety
+  http_parser: ^4.0.0
+  meta: ^1.3.0
+  path: ^1.8.0
+  pedantic: ^1.10.0
 
 dev_dependencies:
-  shelf: any
+  shelf: ^1.0.0-nullsafety.0
   test: ^1.16.0-nullsafety.4
-
-dependency_overrides:
-  shelf:
-    git: git://github.com/dart-lang/shelf.git