Bump pytest-cov from 2.12.0 to 2.12.1

Bumps [pytest-cov](https://github.com/pytest-dev/pytest-cov) from 2.12.0 to 2.12.1.
- [Release notes](https://github.com/pytest-dev/pytest-cov/releases)
- [Changelog](https://github.com/pytest-dev/pytest-cov/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest-cov@v2.12.0...v2.12.1)

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

requirements/dev.txt

@@ -4,17 +4,11 @@
 #
 #    pip-compile --output-file=requirements/dev.txt requirements/dev.in
 #
-atomicwrites==1.4.0
-    # via pytest
 attrs==21.2.0
     # via pytest
 click==8.0.0
     # via pip-tools
-colorama==0.4.4
-    # via
-    #   click
-    #   pytest
-coverage[toml]==5.5
+coverage==5.5
     # via pytest-cov
 iniconfig==1.1.1
     # via pytest
@@ -28,11 +22,11 @@ pluggy==0.13.1
     # via pytest
 py==1.10.0
     # via pytest
-pylibmc==1.6.1; platform_system != 'Windows'
+pylibmc==1.6.1
     # via -r requirements/dev.in
 pyparsing==2.4.7
     # via packaging
-pytest-cov==2.12.0
+pytest-cov==2.12.1
     # via -r requirements/dev.in
 pytest==6.2.4
     # via
@@ -44,9 +38,9 @@ six==1.16.0
     # via python-memcached
 toml==0.10.2
     # via
-    #   coverage
     #   pep517
     #   pytest
+    #   pytest-cov
 
 # The following packages are considered to be unsafe in a requirements file:
 # pip