tests: use coverage < 7.6.2 with pypy 3.10

see also:
nedbat/coveragepy#1902

Bug: T380732
Change-Id: I3a8942e91ef3a30f4b4fe80392030bd88c82040a

.github/workflows/pywikibot-ci.yml

@@ -78,7 +78,7 @@ jobs:
         python -m pip install --upgrade pip
         pip --version
         # T380732
-        pip install "coverage !=7.6.2,!=7.6.3,!=7.6.4,!=7.6.5,!=7.6.6,!=7.6.7,!=7.6.8; implementation_name=='pypy' and python_version=='3.10'"
+        pip install "coverage < 7.6.2; implementation_name=='pypy' and python_version=='3.10'"
         if [ -f dev-requirements.txt ]; then pip install -r dev-requirements.txt; fi
         if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
         pip install wikitextparser