chore!: remove Vertex AI Task Store integration (#999)

It can not be used at the moment, will be readded after 1.0 release.

Author: ishymko

README.md

@@ -68,7 +68,6 @@ Install the core SDK and any desired extras using your preferred package manager
 | **gRPC Support**         | `uv add "a2a-sdk[grpc]"`                   | `pip install "a2a-sdk[grpc]"`                |
 | **OpenTelemetry Tracing**| `uv add "a2a-sdk[telemetry]"`              | `pip install "a2a-sdk[telemetry]"`           |
 | **Encryption**           | `uv add "a2a-sdk[encryption]"`             | `pip install "a2a-sdk[encryption]"`          |
-| **Vertex AI Task Store** | `uv add "a2a-sdk[vertex]"`                 | `pip install "a2a-sdk[vertex]"`              |
 |                          |                                            |                                              |
 | **Database Drivers**     |                                            |                                              |
 | **PostgreSQL**           | `uv add "a2a-sdk[postgresql]"`             | `pip install "a2a-sdk[postgresql]"`          |

pyproject.toml

@@ -43,7 +43,6 @@ mysql = ["sqlalchemy[asyncio,aiomysql]>=2.0.0"]
 signing = ["PyJWT>=2.0.0"]
 sqlite = ["sqlalchemy[asyncio,aiosqlite]>=2.0.0"]
 db-cli = ["alembic>=1.14.0"]
-vertex = ["google-cloud-aiplatform>=1.140.0"]
 
 sql = ["a2a-sdk[postgresql,mysql,sqlite]"]
 
@@ -55,7 +54,6 @@ all = [
   "a2a-sdk[telemetry]",
   "a2a-sdk[signing]",
   "a2a-sdk[db-cli]",
-  "a2a-sdk[vertex]",
 ]
 
 [project.urls]