Update dependency pytest-cov to v6

pyproject.toml

@@ -34,7 +34,7 @@ sentencepiece = "^0.2.0"
 protobuf = "^5.27.2"
 
 pytest = { version = "8.3.4", optional = true, extras = ["test"] }
-pytest-cov = { version = "5.0.0", optional = true, extras = ["test"] }
+pytest-cov = { version = "6.0.0", optional = true, extras = ["test"] }
 pdbpp = {version = "^0.10.3", optional = true, extras = ["test"]}
 ruff = {version = ">=0.5.1,<0.8.0", optional = true, extras = ["test"]}
 black = {version = "^24.3.0", optional = true, extras = ["test"]}