pkg:dart_internal bump support Dart SDK version

Also shorten description

Change-Id: Ida9c7ba0f8c6beb10f218ba53803352b469c7a83
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/196044
Reviewed-by: Nate Bosch <nbosch@google.com>
Reviewed-by: Bob Nystrom <rnystrom@google.com>
Commit-Queue: Kevin Moore <kevmoo@google.com>

pkg/dart_internal/CHANGELOG.md

@@ -1,4 +1,8 @@
-## 0.1.12-nullsafety.1
+## 0.2.1
+
+- Support the latest Dart SDK.
+
+## 0.2.0
 
 - Support the latest Dart SDK.
 

pkg/dart_internal/pubspec.yaml

@@ -1,19 +1,12 @@
 name: dart_internal
-version: 0.2.0
+version: 0.2.1
 repository: https://github.com/dart-lang/sdk/tree/master/pkg/dart_internal
-description: >
+description: >-
   This package is not intended for wide use. It provides a temporary API to
   solve the problem: "Given an object some generic type A, how do I construct an
   instance of generic type B with the same type argument(s)?"
 
-  This is necessary in a few rare places in order to migrate existing code to
-  Dart 2's stronger type system. Eventually, the hope is to have direct
-  language support for solving this problem but we don't have time to get that
-  into 2.0, so this package is provided as a temporary workaround.
-
-  We will very likely remove support for this in a later version of Dart.
-
 environment:
   # Restrict the upper bound so that we can remove support for this in a later
   # version of the SDK without it being a breaking change.
-  sdk: ">=2.12.0-0 <2.13.0"
+  sdk: ">=2.12.0 <2.15.0"