Make "y/N" prompt consistent with others

This yes/no prompt used "[y|N]". Others use "(y/N)":

https://github.com/search?q=repo%3Apyenv%2Fpyenv+%2F%5B%5C%28%5C%5B%5Dy%5B%5C%2F%5C%7C%5Dn%2F&type=code

https://github.com/search?q=repo%3Apyenv%2Fpyenv-virtualenv+%2F%5B%5C%28%5C%5B%5Dy%5B%5C%2F%5C%7C%5Dn%2F&type=code

plugins/python-build/bin/pyenv-uninstall

@@ -75,7 +75,7 @@ uninstall-python() {
       exit 1
     fi
 
-    read -p "pyenv: remove $PREFIX? [y|N] "
+    read -p "pyenv: remove $PREFIX? (y/N) "
     case "$REPLY" in
     y | Y | yes | YES ) ;;
     * ) exit 1 ;;