[Docs] Suggest using collectstatic --clear

docs/admin/10_install.rst

@@ -147,7 +147,7 @@ After that, you can install the aleksis meta-package, or only `aleksis-core`:
 .. code-block:: shell
    pip3 install --break-system-packages aleksis
    aleksis-admin vite build
-   aleksis-admin collectstatic
+   aleksis-admin collectstatic --clear
    aleksis-admin migrate
    aleksis-admin createinitialrevisions
 

docs/dev/01_setup.rst

@@ -91,7 +91,7 @@ All three steps can be done with the ``poetry shell`` command and
 
   ALEKSIS_maintenance__debug=true ALEKSIS_database__password=aleksis poetry shell
    poetry run aleksis-admin vite build
-   poetry run aleksis-admin collectstatic
+   poetry run aleksis-admin collectstatic --clear
    poetry run aleksis-admin compilemessages
    poetry run aleksis-admin migrate
    poetry run aleksis-admin createinitialrevisions