Bump fonttools from 4.14.0 to 4.15.0

Bumps [fonttools](https://github.com/fonttools/fonttools) from 4.14.0 to 4.15.0.
- [Release notes](https://github.com/fonttools/fonttools/releases)
- [Changelog](https://github.com/fonttools/fonttools/blob/master/NEWS.rst)
- [Commits](fonttools/fonttools@4.14.0...4.15.0)

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

Author: dependabot[bot]

requirements.txt

@@ -11,7 +11,7 @@ async-timeout==3.0.1      # via aiohttp
 attrs==20.2.0             # via aiohttp
 cffi==1.14.3              # via pycares
 chardet==3.0.4            # via aiohttp
-fonttools==4.14.0         # via fdiff (setup.py)
+fonttools==4.15.0         # via fdiff (setup.py)
 idna==2.10                # via yarl
 multidict==4.7.6          # via aiohttp, yarl
 pycares==3.1.1            # via aiodns