chore: bump suggested Lean version for making new projects (#729)

The recent Lean releases have added useful functionality to the `lake
new ... math` template, so suggest to use a newer version.

Note that the version only affects the initial project generation and
not its dependencies: `lake` will automatically install the latest
Mathlib as a dependency.

Author: Vierkantor

templates/install/project.md

@@ -75,7 +75,7 @@ We will now create a new project depending on mathlib. The following
 commands should be typed in a terminal.
 
 * Go to a folder where you want to create a project in a subfolder
-  `my_project`, and type `lake +leanprover/lean4:nightly-2024-04-24 new my_project math`. Do not worry about the date in the previous command, it ensures you will use a sufficiently recent version of `lake` but has no impact on the version of `lean` your project will use. If you get an
+  `my_project`, and type `lake +v4.24.0 new my_project math`. Do not worry about the version in the previous command, it ensures you will use a sufficiently recent version of `lake` but has no impact on the version of `lean` your project will use. If you get an
   error message saying `lake` is an unknown command and
   you have not logged in since you installed Lean, then
   you may need to first type `source ~/.profile` or `source ~/.bash_profile`.