build(deps): bump twisted from 19.2.1 to 19.7.0 in /maint

Bumps [twisted](https://github.com/twisted/twisted) from 19.2.1 to 19.7.0.
- [Release notes](https://github.com/twisted/twisted/releases)
- [Changelog](https://github.com/twisted/twisted/blob/trunk/NEWS.rst)
- [Commits](https://github.com/twisted/twisted/compare/twisted-19.2.1...twisted-19.7.0)

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

maint/requirements.txt

@@ -1,14 +1,14 @@
 alabaster==0.7.12
 appdirs==1.4.3
 attrs==19.1.0
-Automat==0.7.0
-Babel==2.6.0
+automat==0.7.0
+babel==2.6.0
 black==19.3b0
 bleach==3.1.0
 certifi==2019.3.9
 cffi==1.12.3
 chardet==3.0.4
-Click==7.0
+click==7.0
 constantly==15.1.0
 coverage==4.5.3
 docutils==0.14
@@ -19,11 +19,11 @@ hyperlink==19.0.0
 idna==2.8
 imagesize==1.1.0
 incremental==17.5.0
-Jinja2==2.10.1
-MarkupSafe==1.1.1
+jinja2==2.10.1
+markupsafe==1.1.1
 mccabe==0.6.1
-mypy==0.701
 mypy-extensions==0.4.1
+mypy==0.630
 packaging==19.0
 pep8==1.7.1
 pkginfo==1.5.0.1
@@ -34,17 +34,17 @@ pycodestyle==2.5.0
 pycparser==2.19
 pycurl==7.43.0.2
 pyflakes==2.1.1
-Pygments==2.3.1
-PyHamcrest==1.9.0
+pygments==2.3.1
+pyhamcrest==1.9.0
 pyparsing==2.4.0
 pytz==2019.1
 readme-renderer==24.0
-requests==2.21.0
 requests-toolbelt==0.9.1
+requests==2.21.0
 six==1.12.0
 snowballstemmer==1.2.1
-Sphinx==2.0.1
 sphinx-rtd-theme==0.4.3
+sphinx==2.0.1
 sphinxcontrib-applehelp==1.0.1
 sphinxcontrib-asyncio==0.2.0
 sphinxcontrib-devhelp==1.0.1
@@ -56,8 +56,8 @@ toml==0.10.0
 tox==3.9.0
 tqdm==4.31.1
 twine==1.13.0
-Twisted==19.2.1
-typed-ast==1.3.5
+twisted==19.7.0
+typed-ast==1.1.2
 urllib3==1.24.3
 virtualenv==16.5.0
 webencodings==0.5.1