Update file install-grub

This MR fixes the condition check [[ "$fallback_is_same" == "true" ]]which prevents the script from replacing the fallback efi stub.

Evaluating the condition fallback_is_same should equal false instead of true to allow for replacing if the files are not identical

if [[ "$grub_type" == "EFI" ]] && [[ -e "$efi_source_file" ]] && [[ -e "$efi_target_file" ]] \
     && [[ "$fallback_is_same" == "false" ]] && [[ "$failed_update" == "false" ]]; then
    echo "Update UEFI Fallback file: $efi_source_file"
    $interactive && yes_no
    cp "$efi_source_file" "$efi_target_file"
fi

At the same time a minor formatting issues when printing the _grub_install command variable.

See https://forum.manjaro.org/t/your-booted-entry-uefi-os-is-not-the-same-as-manjaro/180702/19?u=linux-aarhus