[extension_google_sign_in] Drop old Flutter versions (#2320)

Author: stuartmorgan-g

packages/extension_google_sign_in_as_googleapis_auth/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 2.0.6
+
+* Drops support for Flutter <2.8.
+
 ## 2.0.5
 
 * Updates README to reference the correct github URL.

packages/extension_google_sign_in_as_googleapis_auth/example/pubspec.yaml

@@ -4,7 +4,7 @@ publish_to: none
 
 environment:
   sdk: ">=2.12.0 <3.0.0"
-  flutter: ">=1.20.0"
+  flutter: ">=2.8.0"
 
 dependencies:
   extension_google_sign_in_as_googleapis_auth:

packages/extension_google_sign_in_as_googleapis_auth/pubspec.yaml

@@ -8,11 +8,11 @@ name: extension_google_sign_in_as_googleapis_auth
 description: A bridge package between google_sign_in and googleapis_auth, to create Authenticated Clients from google_sign_in user credentials.
 repository: https://github.com/flutter/packages/tree/main/packages/extension_google_sign_in_as_googleapis_auth
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+extension_google_sign_in_as_googleapis_auth%22
-version: 2.0.5
+version: 2.0.6
 
 environment:
   sdk: ">=2.12.0 <3.0.0"
-  flutter: ">=1.20.0"
+  flutter: ">=2.8.0"
 
 dependencies:
   flutter: