docs(readme): update readme broken-links.

- [x] remove broken link line 58
  - Manage test dependencies with pytest fixtures. ~~<https://pytest.org/en/latest/fixture.html\>\~\~_
  - Manage test dependencies with pytest fixtures. <https://pytest.org/en/latest/how-to/fixtures.html\>_
- [x] remove broken line line 62
  - Make use of other pytest plugins <https://pytest.org/en/latest/how-to/plugins.html\>.
- [x] run test
  | Test | Result |
  | ----------- | :-----------: |
  | tests/test_asserts.py  |[0%] |
  | tests/test_database.py  | [5%] |
  | tests/test_environment.py  |    [10%] |
  | tests/test_fixtures.py  |  [17%] |
  | tests/test_unittest.py  | [21%] |
  | tests/test_database.py  | [24%] |
  | tests/test_fixtures.py  | [26%] |
  | tests/test_asserts.py   | [26%] |
  | tests/test_database.py  |[ 39%] |
  | tests/test_db_access_in_repr.py  | [40%] |
  | tests/test_db_setup.py  | [47%] |
  | tests/test_django_configurations.py  | [49%] |
  | tests/test_django_settings_module.py  | [59%] |
  | tests/test_doctest.txt  | [59%] |
  | tests/test_environment.py  | [65%] |
  | tests/test_fixtures.py  | [83%] |
  | tests/test_initialization.py  | [83%] |
  | tests/test_manage_py_scan.py  | [88%] |
  | tests/test_unittest.py  | [94%] |
  | tests/test_urls.py  | [96%] |
  | tests/test_without_django_loaded.py  | [100%] |
Fixes pytest-dev/pytest-django #914

README.rst

@@ -55,11 +55,11 @@ Why would I use this instead of Django's `manage.py test` command?
 Running your test suite with pytest-django allows you to tap into the features
 that are already present in pytest. Here are some advantages:
 
-* `Manage test dependencies with pytest fixtures. <https://pytest.org/en/latest/fixture.html>`_
+* `Manage test dependencies with pytest fixtures. <https://pytest.org/en/latest/how-to/fixtures.html>`_
 * Less boilerplate tests: no need to import unittest, create a subclass with methods. Write tests as regular functions.
 * Database re-use: no need to re-create the test database for every test run.
 * Run tests in multiple processes for increased speed (with the pytest-xdist plugin).
-* Make use of other `pytest plugins <https://pytest.org/en/latest/plugins.html>`_.
+* Make use of other `pytest plugins <https://pytest.org/en/latest/how-to/plugins.html>`_.
 * Works with both worlds: Existing unittest-style TestCase's still work without any modifications.
 
 See the `pytest documentation <https://pytest.org/en/latest/>`_ for more information on pytest itself.