Update docs URL for themes

This was linking to a page that no longer exists and redirects to the old 2.x docs.

Author: graygilmore

README.md

@@ -41,7 +41,7 @@ To work with themes, the CLI needs to be installed globally with:
 
 You can also use do it through Homebrew on macOS: `brew tap shopify/shopify && brew install shopify-cli`
 
-Learn more in the docs: [Shopify CLI for themes](https://shopify.dev/docs/themes/tools/cli)
+Learn more in the docs: [Shopify CLI for themes](https://shopify.dev/docs/storefronts/themes/tools/cli)
 
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