chore: exclude autogenerated .coveragerc (#1510)

Author: parthea

owlbot.py

@@ -37,6 +37,7 @@
     s.move(
         [library],
         excludes=[
+            ".coveragerc",
             "docs/**/*",
             "scripts/fixup*.py",
             "setup.py",
@@ -108,12 +109,6 @@
 
 """)
 
-s.replace(
-    ".coveragerc",
-    "omit =",
-    """omit =
-  .nox/*""")
-
 python.py_samples(skip_readmes=True)
 
 # Use a python runtime which is available in the owlbot post processor here