minor #6825 update cache and logs folder locations (georgiana-gligor)

This PR was submitted for the 3.1 branch but it was merged into the 3.0 branch instead (closes #6825).

Discussion
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update `cache` and `logs` folder locations

Since Sy3 they are under `var` instead of `app`.

Commits
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396cf06 update `cache` and `logs` folder locations

Author: wouterj

setup/file_permissions.rst

@@ -31,8 +31,8 @@ needed permissions:
 
 .. code-block:: bash
 
-    $ rm -rf app/cache/*
-    $ rm -rf app/logs/*
+    $ rm -rf var/cache/*
+    $ rm -rf var/logs/*
 
     $ HTTPDUSER=`ps axo user,comm | grep -E '[a]pache|[h]ttpd|[_]www|[w]ww-data|[n]ginx' | grep -v root | head -1 | cut -d\  -f1`
     $ sudo chmod -R +a "$HTTPDUSER allow delete,write,append,file_inherit,directory_inherit" var