pyenv: run pyenv init with --no-rehash (ohmyzsh#8917)

Add --no-rehash to the pyenv init command, which was removed in [ohmyzsh#4492].

The rehash was likely disabled because it can affect shell startup times.
It should only be necessary when installing or removing Python versions.

See [pyenv/pyenv#784] and [sorin-ionescu/prezto#1603] for more detail.

[ohmyzsh#4492]: ohmyzsh#4492
[pyenv/pyenv#784]: pyenv/pyenv#784
[sorin-ionescu/prezto#1603]: sorin-ionescu/prezto#1603

plugins/pyenv/pyenv.plugin.zsh

@@ -29,7 +29,7 @@ if [[ $FOUND_PYENV -ne 1 ]]; then
 fi
 
 if [[ $FOUND_PYENV -eq 1 ]]; then
-    eval "$(pyenv init - zsh)"
+    eval "$(pyenv init - --no-rehash zsh)"
     if (( $+commands[pyenv-virtualenv-init] )); then
         eval "$(pyenv virtualenv-init - zsh)"
     fi