[enh] Simplify by removing subprocess + add comment

scripts/upgrade

@@ -230,12 +230,9 @@ then
     # See https://www.dokuwiki.org/install:unused_files
     if [ -f "$final_path/data/deleted.files" ]; then
 
-        # Use a "sub process" to start a new shell to run these commands
-        # Allow to use only one "cd" and to be more efficent
-        (
-            # Move to the dokuwiki installation folder so the "official" commands can be used without adaptation
-            cd $final_path
-
+        # Feed output of grep[...] line by line to 'ynh_secure_remove'
+        # 'ynh_secure_remove' can only work file by file. Cannot work with a list
+        # This is a (complicated) workaround this limitation
         while IFS= read -r line; do
 
             # Added this test to reduce the spam printed by helper to the user in the webadmin.
@@ -269,9 +266,6 @@ then
         
         ###grep --null --extended-regexp --invert-match '^($|#)' data/deleted.files > toto.list
         ###xargs --null --verbose --max-args=1 --arg-file=toto.list ynh_secure_remove 2>&1
-
-
-        )
 fi
 
     # TODO Taken from old "upgrade" script. Should check if it is needed and what it does