test: drop majyk per-lang-version coverage level (googleapis#12)

Closes googleapis#11.

Author: tseaver

noxfile.py

@@ -41,7 +41,7 @@ def default(session):
         "--cov-append",
         "--cov-config=.coveragerc",
         "--cov-report=",
-        "--cov-fail-under=97",
+        "--cov-fail-under=0",
         os.path.join("tests", "unit"),
         *session.posargs
     )
@@ -126,4 +126,4 @@ def docs(session):
         os.path.join("docs", "_build", "doctrees", ""),
         os.path.join("docs", ""),
         os.path.join("docs", "_build", "html", ""),
-    )
+    )