Revert "termux_step_create_datatar.sh: add data/ to tar instead of ./"

Unfortunately this does not play nicely with aptly, see
https://github.com/termux/termux-packages/pull/7335#issuecomment-904202191.

This reverts commit b7e6ef9970.

scripts/build/termux_step_create_datatar.sh

@@ -4,5 +4,5 @@ termux_step_create_datatar() {
 		rm -rf data
 	fi
 
-	tar -cJf "$TERMUX_PKG_PACKAGEDIR/data.tar.xz" -H gnu data
+	tar -cJf "$TERMUX_PKG_PACKAGEDIR/data.tar.xz" -H gnu .
 }