Fix links of posts, notes, and tags/%s directories

[hiroyaonoe]

Issue

https://toha-guides.netlify.app/posts is going to be redirected to https://toha-guides.netlify.app/posts/ because posts is a directory. notes and tags/%s are also the same.
There are such redirect links on some pages. For performance, it's not preferred to redirect them.

Description

This PR correct posts, notes and tags/%s to posts/, notes/ and tags/%s/

Test Evidence

Their links are going to be redirected to the correct pages, so there is no change in their behavior.
For example, the Posts link at the navbar in https://toha-guides.netlify.app/ will change from https://toha-guides.netlify.app/posts into https://toha-guides.netlify.app/posts/, but Both destination pages will be the same.

[hossainemruz]

Thank you @hiroyaonoe