docs: update alias in tutorial to not use public_heads() revset

We don't update public heads very well yet and I'd like to take a
shortcut and simply not have care about public heads for now.

docs/tutorial.md

@@ -172,13 +172,12 @@ It's the root commit of every repo. The `root` symbol in the revset matches it.)
 There are also operators for getting the parents (`:foo`), children `foo:`,
 ancestors (`,,foo`), descendants (`foo,,`), DAG range (`foo,,bar`, like
 `git log --ancestry-path`), range (`foo,,,bar`, like Git's `foo..bar`). There
-are also a few more functions, such as `public_heads()`, which is the set of
-revisions that have Git remote-tracking branches pointing to them, except those
-that are ancestors of other revisions in the set. Let's define an alias based on
-that by adding the following to `~/.jjconfig`:
+are also a few more functions, such as `heads(<set>)`, which filters out
+revisions in the input set if they're ancestors of other revisions in the set.
+Let's define an alias based on that by adding the following to `~/.jjconfig`:
 ```
 [alias]
-l = ["log", "-r", "(public_heads(),,,@),,"]
+l = ["log", "-r", "(heads(remote_branches()),,,@),,"]
 ```
 
 The alias lets us run `jj l` to see the commits we have created between public