Bump aiosignal from 1.1.2 to 1.2.0 (#107)

Bumps [aiosignal](https://github.com/aio-libs/aiosignal) from 1.1.2 to 1.2.0.
- [Release notes](https://github.com/aio-libs/aiosignal/releases)
- [Changelog](https://github.com/aio-libs/aiosignal/blob/master/CHANGES.rst)
- [Commits](aio-libs/aiosignal@v1.1.2...v1.2.0)

---
updated-dependencies:
- dependency-name: aiosignal
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

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

requirements/base.txt

@@ -1,7 +1,7 @@
 -r multidict.txt
 # required c-ares will not build on windows and has build problems on Macos Python<3.7
 aiodns==3.0.0; sys_platform=="linux" or sys_platform=="darwin" and python_version>="3.7"
-aiosignal==1.1.2
+aiosignal==1.2.0
 async-timeout==4.0.0a3
 asynctest==0.13.0; python_version<"3.8"
 Brotli==1.0.9