getting started code format (#978)

Summary:
Pull Request resolved: #978

pip install in separate code block

Reviewed By: dbort

Differential Revision: D50350054

fbshipit-source-id: 1f935b579afa3ca270afef889ee38852a51ec316

Author: lucylq

docs/source/getting-started-setup.md

@@ -209,8 +209,10 @@ all the operators and backends.
 
 You will need the following prerequisits for this section:
 
-* The `zstd` command line tool — install by running `pip3 install zstd`.
-
+* The `zstd` command line tool — install by running
+   ```bash
+   pip3 install zstd
+   ```
 * Version `2023-07-18` of the `buck2` commandline tool — you can download a
   prebuilt archive for your system from [the Buck2
   repo](https://github.com/facebook/buck2/releases/tag/2023-07-18). Note that