Bump multidict from 4.7.6 to 5.0.0 (#5036)

Bumps [multidict](https://github.com/aio-libs/multidict) from 4.7.6 to 5.0.0.
- [Release notes](https://github.com/aio-libs/multidict/releases)
- [Changelog](https://github.com/aio-libs/multidict/blob/master/CHANGES.rst)
- [Commits](aio-libs/multidict@v4.7.6...v5.0.0)

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

requirements/ci-wheel.txt

@@ -6,7 +6,7 @@ cchardet==2.1.6
 chardet==3.0.4
 coverage==5.3
 gunicorn==20.0.4
-multidict==4.7.6
+multidict==5.0.0
 pytest==5.4.2
 pytest-cov==2.10.1
 pytest-mock==3.3.1

setup.py

@@ -53,7 +53,7 @@
 install_requires = [
     'attrs>=17.3.0',
     'chardet>=2.0,<4.0',
-    'multidict>=4.5,<5.0',
+    'multidict>=4.5,<6.0',
     'async_timeout>=4.0a2,<5.0',
     'yarl>=1.0,<2.0',
     'idna-ssl>=1.0; python_version<"3.7"',