Fix the install.sh script (this is plain sh, not bash...)

install.sh

@@ -4,7 +4,7 @@ INSTALL_FILES="animation.png arise-theme.plymouth arise-theme.script background.
 INSTALL_FOLDER="/use/share/plymouth/themes"
 THEME_FOLDER="$INSTALL_FOLDER/arise-theme"
 
-function die() {
+die() {
     echo "$*"
     exit 1
 }