Update pytest-cov requirement from <4.2,>=4.0 to >=4.0,<5.1

Updates the requirements on [pytest-cov](https://github.com/pytest-dev/pytest-cov) to permit the latest version.
- [Changelog](https://github.com/pytest-dev/pytest-cov/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest-cov@v4.0.0...v5.0.0)

---
updated-dependencies:
- dependency-name: pytest-cov
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

pyproject.toml

@@ -81,7 +81,7 @@ testing-basic = [
     "freezegun>=1.1.0",
     "pytest-asyncio==0.23.6",
     "certomancer==0.12.*",
-    "pytest-cov>=4.0,<4.2",
+    "pytest-cov>=4.0,<5.1",
     "backports.zoneinfo[tzdata];python_version<\"3.9\"",
 ]
 testing = [
@@ -95,7 +95,7 @@ live-test = [
     "pytest-aiohttp~=1.0.4",
     "certomancer-csc-dummy==0.3.0",
     "certomancer[web-api]==0.12.*",
-    "pytest-cov>=4.0,<4.2",
+    "pytest-cov>=4.0,<5.1",
 ]
 mypy = [
     "pyHanko[pkcs11,xmp,opentype,image-support,async-http,extra-pubkey-algs,etsi]",