Remove completion feature from enhancd

[babarot]

WHAT

Remove completion feature from enhancd to solve #172

WHY

I've added this feature #90 to follow zsh-interactive-cd style completion in enhancd but currently I'm facing these problems:

• sometimes it looks to make bugs native cd completion #172
• it's difficult to maintain these codes because completion feature is complex shell script

Now both plugins enhacd and zsh-interactive-cd can coexist in the same environment (I've tried it out). So those who get troubles by deleting this feature can use this plugin to cover this change.

[babarot]

Test:

Just enter cd <tab>

After installed https://github.com/changyuheng/zsh-interactive-cd and then, enter cd <tab>

YAML I used for testing is here:

github:
- name: b4b4r07/enhancd
  owner: b4b4r07
  repo: enhancd
  branch: babarot/remove-completion
  plugin:
    sources:
    - init.sh
- name: changyuheng/zsh-interactive-cd
  owner: changyuheng
  repo: zsh-interactive-cd
  plugin:
    sources:
    - '*.zsh'
  depends-on:
  - zsh