Update default models to newer versions (#31415)

Follow up to: https://github.com/zed-industries/zed/pull/31209
Changes default models across multiple providers:
- Zed.dev Default Models in settings: claude-3-7-sonnet-latest →
claude-4-sonnet-latest
- Bedrock Default Model: Claude 3.5 Sonnet v2 → Claude Sonnet 4
- Google AI Default Fast Model: Gemini 1.5 Flash → Gemini 2.0 Flash

Release Notes:

- N/A

assets/settings/default.json

@@ -729,14 +729,14 @@
       // The provider to use.
       "provider": "zed.dev",
       // The model to use.
-      "model": "claude-3-7-sonnet-latest"
+      "model": "claude-4-sonnet"
     },
     // The model to use when applying edits from the agent.
     "editor_model": {
       // The provider to use.
       "provider": "zed.dev",
       // The model to use.
-      "model": "claude-3-7-sonnet-latest"
+      "model": "claude-4-sonnet"
     },
     // Additional parameters for language model requests. When making a request to a model, parameters will be taken
     // from the last entry in this list that matches the model's provider and name. In each entry, both provider
@@ -756,7 +756,7 @@
       // To set parameters for a specific provider and model:
       // {
       //   "provider": "zed.dev",
-      //   "model": "claude-3-7-sonnet-latest",
+      //   "model": "claude-4-sonnet",
       //   "temperature": 1.0
       // }
     ],