chore(librarian): reduce diff in google-cloud-iam (#14718)

Towards googleapis/librarian#762

Author: parthea

packages/google-cloud-iam/.OwlBot.yaml

@@ -4,8 +4,8 @@ branch = True
 [report]
 show_missing = True
 omit =
-    google/cloud/iam_credentials/__init__.py
-    google/cloud/iam_credentials/gapic_version.py
+    google/cloud/iam/__init__.py
+    google/cloud/iam/gapic_version.py
 exclude_lines =
     # Re-enable the standard pragma
     pragma: NO COVER

packages/google-cloud-iam/.coveragerc

@@ -28,9 +28,7 @@
 
 version = None
 
-with open(
-    os.path.join(package_root, "google/cloud/iam_credentials/gapic_version.py")
-) as fp:
+with open(os.path.join(package_root, "google/cloud/iam/gapic_version.py")) as fp:
     version_candidates = re.findall(r"(?<=\")\d+.\d+.\d+(?=\")", fp.read())
     assert len(version_candidates) == 1
     version = version_candidates[0]