Remove stale unreleased-extra notes from READMEs

The google-genai and strands-agents extras of temporalio shipped in 1.31,
which pyproject.toml already requires, so `uv sync --group ...` is enough.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: brianstrauch

google_genai/README.md

@@ -25,12 +25,6 @@ These samples demonstrate the [Temporal Google GenAI plugin](https://github.com/
    uv sync --group google-genai
    ```
 
-   > The `google-genai` extra of `temporalio` is shipping in an upcoming release. Until then, install the SDK from the source checkout:
-   >
-   > ```bash
-   > uv pip install -e ../sdk-python --extra google-genai --extra pydantic
-   > ```
-
 2. Configure credentials. Most samples use the Gemini Developer API and read an API key from the environment:
 
    ```bash

strands_plugin/README.md

@@ -24,12 +24,6 @@ These samples demonstrate the [Temporal Strands plugin](https://github.com/tempo
    uv sync --group strands-agents
    ```
 
-   > The `strands` extra of `temporalio` is shipping in an upcoming release. Until then, install the SDK from the strands branch:
-   >
-   > ```bash
-   > uv pip install -e ../sdk-python --extra strands-agents --extra pydantic
-   > ```
-
 2. Configure AWS credentials. The samples use the plugin's default `BedrockModel()`, which picks up the standard AWS SDK credential chain. Make sure the credentials grant access to a Bedrock model in your selected region (e.g., `us-west-2`).
 
    ```bash