It was introduced to work around React Router v6's issue of not encoding
parameters in the generatePath function. However, after migrating to v7,
tests began failing due to double encoding. This revealed that React
Router v7 already handles encoding parameters in generatePath. See
remix-run/react-router#13530

Thus, this commit reverts the changes made in
#2576

## Problem

React Router v7 was released almost a year now (see
https://reactrouter.com/changelog#v700), but it has not been updated in
Agama yet. In addition to the obvious benefit of keeping dependencies
up-to-date, updating it might help to address some limitations we have
found with the v6 version, like
06d858c

## Solution

Migrate React Router dependency to its latest version.

## Testing

- Adapted existing tests.

## Notes

This migration has been straightforward, and as of now, Agama is using
Data Mode (see https://reactrouter.com/start/modes). However, this could
change in the future if we find advantages in switching to Declarative
or Framework Mode. Before making any decisions, we’ll need to work on
`src/App.tsx` along with the changes planned for the api-v2 branch that
this PR is based on.

## Documentation


 * https://reactrouter.com/upgrading/v6
*
remix-run/react-router#12363 (comment)
* remix-run/react-router#13530 (`generatePath`
now encodes URL params by default, related to
#2576)
 * https://www.typescriptlang.org/tsconfig/#moduleResolution