chore: Bump temporalio Dep in Temporal Example (#2918)

Version 1.26.0 of `temporalio` comes with sandbox agent support out of
the box. No more need for the temporary vendoring to backport the
functionality into the prior 1.25.x version. That was a temporary
workaround to ensure the example worked on day 1 since we (Temporal) had
to wait on making our release until after this project published 0.14.0
to avoid leaking the feature early.

Author: JasonSteving99

examples/sandbox/extensions/temporal/README.md

@@ -46,12 +46,7 @@ any cloud provider API keys.
    ```
 
 The `just worker` and `just tui` commands automatically install dependencies
-and patch the installed `temporalio` package with vendored sandbox support.
-This patch step is temporary -- the next `temporalio` release will include
-sandbox support natively, at which point the vendored plugin and patch step
-will be removed. Until then, running the Python scripts directly without
-the patch step (i.e. skipping `just worker`/`just tui`) will fail at import
-time.
+before starting.
 
 ## TUI commands