feat: update dependency constraints to sdk: '>=2.18.0 <4.0.0' flutter: '>=3.3.0' (#10946)

Author: Lyokone

Diff for: packages/_flutterfire_internals/pubspec.yaml

@@ -5,8 +5,8 @@ repository: https://github.com/firebase/flutterfire/tree/master/packages/_flutte
 version: 1.2.0
 
 environment:
-  sdk: '>=2.18.0 <3.0.0'
-  flutter: '>=1.12.13+hotfix.5'
+  sdk: '>=2.18.0 <4.0.0'
+  flutter: '>=3.3.0'
 
 dependencies:
   collection: ^1.0.0

Diff for: packages/cloud_firestore/cloud_firestore/example/pubspec.yaml

@@ -2,7 +2,7 @@ name: cloud_firestore_example
 description: Demonstrates how to use the firestore plugin.
 
 environment:
-  sdk: '>=2.18.0 <3.0.0'
+  sdk: '>=2.18.0 <4.0.0'
 
 dependencies:
   cloud_firestore: ^4.6.0