DOC: simplify wording for rye sync after rye add (#986)

This PR improve text in the doc so a new user of rye doesn't miss the need to `rye sync` after adding a dependency to actually install it. I skimmed past the original text so hopefully this will help the next reader.

docs/guide/basics.md

@@ -74,8 +74,8 @@ Use the `add` command to add dependencies to your project.
 rye add "flask>=2.0"
 ```
 
-Note that after `add` you need to run `sync` again to actually install it.  If you
-want to add packages from custom indexes, you have to [configure the source](sources.md)
+Followed by `rye sync` to install the dependency into the virtual environment. 
+If you want to add packages from custom indexes, you have to [configure the source](sources.md)
 first.
 
 ## Listing Dependencies