Redo pull #1687

Fix for case sensitive duplicate domains
The change (https://github.com/pi-hole/pi-hole/pull/1687) was recently undone.

gravity.sh

@@ -367,7 +367,7 @@ gravity_Schwarzschild() {
     # Determine if file has read permissions, as download might have failed
     if [[ -r "${i}" ]]; then
       # Remove windows CRs from file, and append into $matterAndLight
-      tr -d '\r' < "${i}" >> "${piholeDir}/${matterAndLight}"
+      tr -d '\r' < "${i}" | tr '[:upper:]' '[:lower:]' >> "${piholeDir}/${matterAndLight}"
 
       # Ensure that the first line of a new list is on a new line
       lastLine=$(tail -1 "${piholeDir}/${matterAndLight}")