This fixes broken links in the eslint output by removing the trailing full stop.
It also makes the formatting of (the output of) the various rules consistent.

## Documentation / Examples

- [x] Make sure the linting passes by running `yarn lint`

> I don't think this is a bug, nor a feature, nor is it really documentation. 
> It's just a small nuisance that I bumped into and felt compelled to fix.
> I went with documentation as that seems the closest match

## What does this pull request do?

The elslint output of `eslint-plugin-next` contains useful links to the documentation about the various rules.
Unfortunately, on most (but not all) rules, those links are immediately followed by a full stop (`.`).

The terminal (or any parser) has no way of knowing that the full stop is not part of the URL. 
So it includes it and clicking the link leads to a 404 on the nextjs.org website.
 
![eslint](https://user-images.githubusercontent.com/1708494/147452577-43ad4ce7-df75-4d48-ab78-70b9b8212b7e.png)

This PR fixes that by removing the full stop. 

## But a final full stop is better grammar

I considered alternatives (such as [a zero-width space character](https://en.wikipedia.org/wiki/Zero-width_space#Prohibited_in_URLs)) in case the final full stop was part of the style guide or something.

However, as I went through the eslint rules, I notices that the messages for various rules were formatted inconsistently. 
Some with final full stop, some without.

As such, I made the all consistent with this structure:

> [message]. See: [url]

I feel this is a better solution than using the zero-width space as these sort of invisible characters 
in code can be a red flag that something fishy is going on.

I submit this pull request in the hope it will be useful, and a positive contribution to a project I have a great deal of appreciation for.
That being said, I fully understand if people would consider this a non-issue.