build: remove deprecated flags used to skip a repeated deno installation (#57)

Co-authored-by: slack-samples[bot] <169401055+slack-samples[bot]@users.noreply.github.com>

Author: slack-samples[bot]

.devcontainer/Dockerfile

@@ -21,4 +21,4 @@ RUN export PATH="$DENO_INSTALL/bin:$PATH"
 WORKDIR /workspaces
 
 # Install the Slack CLI
-RUN curl -fsSL https://downloads.slack-edge.com/slack-cli/install.sh | bash -s -- -d
+RUN curl -fsSL https://downloads.slack-edge.com/slack-cli/install.sh | bash

.devcontainer/README.md

@@ -30,6 +30,6 @@ file:
 ```
 
 [codespaces]: https://github.com/features/codespaces
-[cli]: https://api.slack.com/automation/cli
+[cli]: https://docs.slack.dev/tools/slack-cli/
 [container]: https://containers.dev/
 [vscode]: https://code.visualstudio.com/docs/devcontainers/containers