Build(deps): update matplotlib requirement from ~=3.3 to ~=3.4 (#160)

Updates the requirements on [matplotlib](https://github.com/matplotlib/matplotlib) to permit the latest version.
- [Release notes](https://github.com/matplotlib/matplotlib/releases)
- [Commits](matplotlib/matplotlib@v3.3.0...v3.4.1)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Matthew Evans <7916000+ml-evs@users.noreply.github.com>

requirements/requirements.txt

@@ -5,4 +5,4 @@ pyyaml~=5.4
 pymongo~=3.11
 numba~=0.52
 tqdm~=4.61
-matplotlib~=3.3
+matplotlib~=3.4