Fix mfrb and mfpub

buildroot/share/git/mfpub

 # Push 'master' to the fork and make a proper PR...
 if [[ $BRANCH == "master" ]]; then
 
-  if [[ $$FORK == "MarlinFirmware" ]]; then
+  if [[ $FORK == "MarlinFirmware" ]]; then
 
     # Allow working directly with the main fork
     git push -f upstream

buildroot/share/git/mfrb

 esac
 
 # If the branch isn't currently the PR target
-if [[ ${INFO[4]} != ${INFO[5]} ]]; then
+if [[ ${INFO[3]} != ${INFO[4]} ]]; then
   git fetch upstream
   git rebase upstream/${INFO[3]} && git rebase -i upstream/${INFO[3]}
 fi