fix(docs): yarn install command in html.mdx (#1901)

Author: terrierscript

apps/docs/components/html.mdx

@@ -27,7 +27,7 @@ yarn add @react-email/components -E
 
 # or get the individual package
 
-pnpm add @react-email/html -E
+yarn add @react-email/html -E
 ```
 
 ```sh pnpm