Remove prompt deprecation warning (#447)

Prompt removal was never done and is not planned anymore

bin/pyenv-sh-activate

@@ -225,9 +225,6 @@ if [ -z "${PYENV_VIRTUALENV_DISABLE_PROMPT}" ]; then
     fi
     ;;
   * )
-    if [ -z "${QUIET}" ]; then
-      echo "pyenv-virtualenv: prompt changing will be removed from future release. configure \`export PYENV_VIRTUALENV_DISABLE_PROMPT=1' to simulate the behavior." 1>&2
-    fi
     cat <<EOS
 export _OLD_VIRTUAL_PS1="\${PS1:-}";
 export PS1="(${venv}) \${PS1:-}";