Bump numpy from 1.18.1 to 1.18.2 (#931)

Bumps [numpy](https://github.com/numpy/numpy) from 1.18.1 to 1.18.2.
- [Release notes](https://github.com/numpy/numpy/releases)
- [Changelog](https://github.com/numpy/numpy/blob/master/doc/HOWTO_RELEASE.rst.txt)
- [Commits](numpy/numpy@v1.18.1...v1.18.2)

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Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
Co-authored-by: Sylvestre Ledru <sledru@mozilla.com>

requirements.txt

@@ -14,4 +14,4 @@ icalendar==4.0.5
 sqlalchemy==1.3.15
 filelock==3.0.12
 alembic==1.4.2
-numpy==1.18.1
+numpy==1.18.2