FIX: remove "exernal-sources" option when running shellcheck

This option caused some checks to be ignored

shellcheck/launch_shellcheck.sh

@@ -14,7 +14,7 @@ fi
 for f in $files; do
     if head "$f" | grep -qE "^# run-shellcheck$"; then
         printf "\e[1;36mRunning shellcheck on: %s  \e[0m\n" "$f"
-        if ! /usr/bin/shellcheck --color=always --external-sources --shell=bash "$f"; then
+        if ! /usr/bin/shellcheck --color=always --shell=bash "$f"; then
             retval=$((retval + 1))
         fi
     fi